Hit stun here applies to both takeurlife (aerial and ground).do you mean anti-air jab or jab when you are both grounded?
What I haven't tested though, is if the 11%/6% thing applies universally, or is dependant on weight of the opponent. Which is probably HIGHLY likely.
So for the time being, say
@ 198% untippered jab-> db Works on Marth,
and @ 66% tippered jab -> db works on Marth.
Explaination:
Marth hits Marth with a tipper jab at 66%, it deals unPRECENDENTED DAMAGE (lol), 28 frames of hit stun.
Marth's Jab:
Hit: 4
End: 27
Hit Stun: 28
Advantage Formula: (4-27) + 28 + 1 (Hit stun applies from after hitlag, i.e. frame 5 of jab)
= +6 frame advantage.
2 Frames to dash and 4 frames for db1.
Oh, and of course take, DI matters.