The simple explanation of how to do these is that you don't need to be that amazing or do a whole pile of killer math. You definitely need to practice a whole pile in training mode to get the aerial CS timing down, which can be easy (up-tilt starter) or very hard (dash starter). The VAST bulk of the cast sits in and around a magic number of 30. If you simply learn how to combo one character, say fox who sits precisely at 30, then you can intuitively adjust a bit to know how to combo all the others.
Subtracting, particularly in the middle of a fight, does not work for me. I am not some sort of savant. I keep a few numbers in my head and the only calculation I do is add 1/10th of Samus' damage to the opponents.
I'm typically always watching for 15, 20 and 30. 15 is the dash -> up-air -> CS, 20 is the grab->up-air->CS and 30 is magic where tons of good stuff can happen out of an up-tilt.
The next and most important thing I recently discovered is about up-tilt. In the video you see tons of people getting up-tilted, are they all "bad" players who can't tech? The answer is no. The key is up-air. If you notice I will FF up-air->up-tilt and it miraculously seems to land.
This comes back to Roach Cake's insistence that I add in this thread the soft-hits of u-air to d-tilt combo. He insisted on it, and despite all my testing in training mode I couldn't get it to true combo, the hitstun is not enough from the small hits.
If you play enough you realize this just "works". The up-B variant as well. It just does. Why? Game says it's not a true combo. This puzzled me for a while. From frame data it makes no sense. It's 11 frames landing lag for up-air and 6 frames to get out d-tilt. That's 17 frames. Anyone with a quick jab, or even just a grab should smack us around. But no, never happens. WHY?
The first part is frame cancelling. Up-air frame cancels something like 99% of the time. It's amazing. This means you go from 11 frames to 4.
The next part is that the opponent is popped up by the soft hits and must land. In smash 4, even if you do absolutely nothing, you incur 4 frames of landing lag. So relative to the opponent because of frame cancelling, you are at zero frame advantage.
But it's better than that. If it was just zero frame advantage little mac could jab you with his frame 1 jab vs. your frame 6 d-tilt. But with enough damage, he can't, at all (my testing, someone else could confirm). Or anyone could get up a shield.
It doesn't happen. Why? Because they are popped up in the air. There are a few frames where they need to go from in the air to landing before landing lag. It's almost exactly 6 by my count for anyone even at 0% (with small growth at high %). So it will not register as a "true" combo, but it is in all practical terms.
Ok, so why does up-tilt work so well? Makes even less sense, it's frame 15 vs. d-tilt's frame 6. Even if soft hits of up-air->dtilt is a frame advantage true combo, surely up-tilt isn't. Even if the first 6 frames are guaranteed that's still 15-6 = 9 frames to play with right?
Can you be knocked out of up-air->up-tilt? Yes, you can, by a perfectly timed fast jab. Can they possibly shield? Yes. Can they possibly tech? Yes. But the window to do so is very very small and it is very ugly if you screw up. Why?
Because of buffering. Buffering is what is slaughtering people. Whether accidental or intentional buffering is making up-air->up-tilt "work". Even good players who try to tech can instead buffer an airdodge, which means 22 frames of landing lag, or they buffer an aeriall, and they are screwed, the game registers them airdodging/attacking into the the ground not the the tech. If you look closely at the video you can see this effect in several places, the bowser (a crazy good player) is most obvious, he pulls out f-air, and he suffers the full landing lag of his aerial and is screwed. What this means is that up-air -> up-tilt is not guaranteed but it's *just short of guaranteed*. It's very very good and means Samus' up-tilt combo game goes from being a theoretical threat to a really significant threat.
So for those interested here's the very detailed breakdown of what you're seeing in the video.
0.24: The RoachCake combo + string. The first b-air is a true combo, the second is a (very tight) string.
0:30 Falcon tries to rapid jab me. DI/SDI to get above him. Use 5-frame up-air combo breaker. I have 20 damage, he has 5 after the up-air, that means effectively 7 damage, enough to knock him into full hitstun from the up-tilt and allow the up-tilt->d-tilt combo. Capt falcon needs a bit of damage on him for up-tilt->dtilt to true combo. The sweetspot would be at 13 damage, 7 is close enough.
0:38 Kirby gets full hitstun from an up-tilt at 0%, so up-tilt->d-tilt is true combo and I punish his d-smash for 26%.
0:40 Same scenario. Zero suit's magic number is 31, the combo sweetspot is -25 = 6 damage, it's well within the range. I hit with the heel in both cases, which gives the best combo follow up window. Dash Up-smash is actually a great string folllow up.
0:47 Falcon is at 32 + 1 = 33, well within the b-air sourspot -> f-ftilt. The b-air lands high but very deep because he misses his dash. He misses the tech on falling prone, the f-tilt lands.
0:50 Falcon at zero, very deep, frame cancels and true combos. I angle it for more damage because I know the % is very low.
0:54 SH N-air approach on pacman is actually quite good. The wi-fi grab is slow, it's quite safe. N-air d-tilt catches him once on shield and once in true combo.
1:07 Same.
1:15 N-air lands high on Ike at 17%. The n-air into dash is just barely not a true combo in this case it's a tight string. The rest of the dash is a true combo. 38 damage total.
1:20 DK rolls into me at the ledge while I short-hop. Regular, non fast-fall multihit of up-air counters the roll and the final hit of up-air leads to a true combo b-air.
1:26 Mario starts at 38 + 4 = 40% damage. From the table his magic number is 35 and that means he's well within range of grab double. 28 damage out of a grab.
1:34 Fox is at 28+5 = 33%. Magic number is 30. He's within range of a grab double. If I tried for grab->up-air->CS I might miss, even as a fast faller. 27 damage out of a grab.
1:45 Sonic is at 0+3 = 3%. His magic number is 31, I can definitely aim for the grab triple. 36 damage to the rodent out of a grab.
2:00 I miss the B-air -> F-tilt, not deep enough. Samus is at 21 + 1 = 22%. Samus magic number is 33 - she is hard to combo despite being a super-heavy weight. Magic - 15 = 18% sweetspot for a dash->up-air->CS. I go for it
and barely get it. This is an unforgiving combo.
2:09 Villager is at 25 + 1 = 26%. Magic number is 29. It should land best circa 19, near the end of the range but connects. True combo, 42 guaranteed damage out of a single grab.
2:16 Lucina is at 16 + 10 = 26%. Magic number is 32. It should land best circa 23, prime range and it connects. Perfect example of rage mechanic understood.
2:22 Pit is at 42 + 5 = 47%. Magic is 33. Uptilt -> FJ -> CS sweetspot 48, bang on. Cross-up up-air, even if he shielded, no shield grab possible. 41 damage.
2:30 TLink is at 45+10 = 55%. Magic is 29. Uptilt -> FJ -> CS sweetspot 44. Near the edge of the combo range, but it works. 40 damage. This was not the best player. He saw the up-tilt and air-dodged into the ground, bad idea.
2:34 MewTwo is at 36 + 5 = 41%. Magic is 25. I can FJ or SH, both are within combo range. I had Mewtwo's number wrong in the OP incidentally, it's 25, not 31, his combo physics are weird due to falling animation.
2:38 TLink is at 65 + 11 = 76%. Magic is 29. D-air -> FJ -> CS within range (it's broad).
2:47 MewTwo is at 76+6 = 82%. He is out of range of up-tilt->DJ-> CS which would sweetspot at 65, tip of the range would be around 75, so he's just a bit beyond. I go for it and hope for a conditioned air-dodge. Bingo.
2:56 Kirby is at 23+11 = 34. Magic is 23. He is out of range of Up-tilt double but just barely and I know this. I hope for a conditioned air-dodge. Bingo.
3:09 People on for-glory who are not Samus mains and switch to Samus to try and beat my own irritate me.
3:12 Kirby cannot be dash tripled - Magic is 23 and dash triples would sweetspot at -8, it's just bad, you're going to get a double in practice. He can on the other hand be up-air tripled, that sweetspots at roughly 12 damage, well within range.
3:20 An example of offensive tracking DI to maintain the combo. At these low % he has very little control but I hunt him down in the air keeping the combo going.
3:30 Another example of offensive DI. Also with Samus at 0% and Falcon at 0% the dash triple lands poorly, sweetspot would be falcon at 8%. Samus with 97% and rage means this combo sweetspots.
3:37 Sonic at 25 + 10 = 35. Magic is 31. Almost perfect. Big damage time! 49%
3:44 Bowser at 25 + 5 = 30. Magic is 41. The reason this true combos is because almost all the hits of up-air land, meaning at the start of the up-tilt he's at 29. It's really even then at the tip of the early end of the combo range but it's true, not a string. 54% all told. This Bowser was insanely good.
3:48 Fox at 32 +2= 34. Magic is 30. Cross-up up-air.
3:58 Jiggly at 20 + 2 = 22. Magic is 19. When you're a light character and you're hit for 50 damage, the set is all but over, there's really no coming back.
The ledge get-up-attack CS tech chase is completely safe on reflector fast fallers (fox, falco) since you fall back off the stage with the CS automatically.
Scream
. And yes, aerial sourspot B-air never combos into another aerial, up-B would be natural best fit but I can't get it to register in any circumstance. The knockback and end-lag are selected specifically to disallow it, as soon as they get enough hitstun they're too far away.
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thanks, are you interested in making a list for customs? I've had several bites but no takers since it's quite a lot of work. 
