How to allow users multiple reservations for one slot?

Is there a widget that:

shows a calendar

allows only certain days to be available on the calendar

allows multiple reservations for one slot from the same user

shows how many spots are left in the class

I need to provide a date selector, only on sundays with a max of 8 people.  When a person registers, they need to be able to purchase up to 8 spots.

I currently have a appointment selector but they cannot select more than one spot and there isn't a calendar.

As I understand, you need a widget, which would show a calendar and had a functionality of Appointment slots. Unfortunately, we do not have such widget at the moment, but I can reccomend to take a look at Quantity Gift Registry widget. 

The Quantity Gift Registry widget would allow you to accept a limited number of items for each option/date, so you could list the dates manually and let your users select them as options. It would also allows multiple reservations for one slot from the same user:

Let us know if you need any other assistance with JotForms.