If a customer registers for a class but isn't marked as attending, you'll see that mentioned when you call up that person's record. It looks like this:
This information may signal that a follow-up on your part is warranted.
Perhaps there was a lapse in marking attendance and the person was actually in class? You can correct this past attendance in Punchpass.
Or perhaps this person had a one-off situation arise?
If reservations without attendance are a habit, you may consider implementing a policy around that.
You can follow up with the customer via email directly from their record in Punchpass.