How do you do the jump in main that saves like 3 seconds o.O

flick high jump im guessing, it sometimes is rng to do in a speedrun edit: there's also a video describing it etter than I can in words:

As mentioned by Blox, it requires rng and skills in order to do it. Once you've mastered it, you can easily get a sub 10 (which requires a lot of grind).