Hi @mehall,

I have limited experience with this feature as a Canvas admin for my institution.  With what I know though, the intention in the scenario you describe is that there would be one appointment slot total at 9am.  If a student from 101 signs up for that slot, there would be no 9am availability any longer for the 102 students.

I hope this info helps!  If you do discover any contrary behavior, please let the community here know!

-Chris