Question regarding invincible ledge dash

[Charlesz]

Can someone who knows what they are talking about explain the timing of how to do this? Every time I've done a wavedash from the ledge with fox I'm usually vulnerable. A prime example of someone really taking advantage of this strategy is Leffen.

 

[Kadano]

Grabbing the ledge grants you 29 frames you can use to drop from the ledge and do stuff afterwards. Because wavelanding is 10 frames and Fox’s second jump accelerates so quickly (it takes 3 frames in most cases to be high enough to waveland), you have a lot of leniency. The most important thing is to let go of the ledge as soon as possible. Then you jump and press L/R and hold 197°/343° on the control stick to waveland with the lowest possible angle.

 

[reverie2]

EDIT: nvm found my answer