How do I count the number of users registered for a specific appointment slot?

We're trying to figure out how many people we've registered for a given slot and have it show in a report, but there doesn't seem to be any way to do that.

Unfortunately, we do not have a report format that automatically groups the selected appointment slot and count the number of submissions per slot.

As a workaround, if you wish to count the number of submissions for a specific time slot, I suggest you make use of the Table's filters.

https://www.jotform.com/help/1009-how-to-use-different-filters-to-easily-manage-your-data-in-jotform-tables