when to reset the timer ?

So my girlfriend and I want to go the longest we can without making me cum, but she still want to use my dick for her pleasure without letting me cum. Though we are using chaster app to have a timer and see the remaining time of my lockup. But I don’t know when do we have to reset the timer to 0 ?

- when I’m unlocked for sex even without cumming ?

- When any drop of cum goes out from me even if it’s a ruined orgasm ?

- when I have a night ejaculation ?

- other…

What do you think about it ? Any idea ?