Hello.
The main purpose of the Booking Calendar is to receive and manage bookings. In Booking Calendar Free version you can activate this option: “Allow unlimited bookings per same day(s):” – “if you want to set any days as available in calendar. Your visitors will be able to make unlimited bookings per same date(s) in calendar and do not see any booked date(s) of other visitors.”
If you need to have some dates as available and some dates as not available, and receive on specific available dates specific number of bookings (please note, this number of bookings will be the same for any available dates), then you need to check the Booking Calendar Business Large version, where is possible to make several reservations per specific FULL date(s) by visitors (not time slots). Please read more about it here https://wpbookingcalendar.com/overview/#capacity
At this version is possible to set capacity of the booking resource, so date(s) in calendar will be available until number of reservations is less then capacity of the booking resource.But in this version is possible to make reservation only for FULL date, not a time slots (time slots in this version only record data in the DB, but do not play any logic in reservation).
Please read more info about the booking resources and how to configure them here https://wpbookingcalendar.com/help/booking-resource/
Also we highly recommend to check this article about different configuration of capacity and availability https://wpbookingcalendar.com/faq/capacity-concept/
Kind Regards.