Reset "countif" after specific date is reached

Some times it happens, another day I couldn't upload a formula because of some combination of signs.

Just wanted to share my solution, not ****, not elegant, but easy...
Instead of having the =countif from 1-8 (which I still cannot manage), I will just put a number in when students attend. As soon as nr 1 is in, cell turns red. If they pay, there is another 1 (paid) that can be selected.

Not very cool, but kind of solves the problem.

Cheers,
Roz