If a customer has a number of appointments on a given day, Versum will display them all in the checkout window so you can complete them collectively.

If you don't want to check out some of them (e.g. because the customer hasn't paid for some of the appointments yet), you can remove the appointments from the list by clicking the X button in the right upper corner of the appointment you want to remove:

Note: This will not delete the appointment, but only remove it from the list.