Double Rolling Sobat --> Sobat Carnival

Trying to do his trial and I’m stuck on level 14. What I don’t understand is how do you get the charge to pull out his super on the first hit of Double Rolling Sobat. How long do you have to charge back to execute his super?

Here’s the motion:

(hold)back, forward + mk(or hk) [the first sobat kick must hit your opponent either clean or they block it, and before the second sobat comes out you do the rest of the motion], back, forward + (any kick)

You don’t need to do a separate charge for the super because that’s how cancels work.