Help with calendar?

Hi. New to Rover. When I go in to manager my calendar, I want to subtract booked services from the max I have selected that I can do. It appears you are only able to adjust the total number of spaces booked but not the ones you have booked. Let's say I can do four walks a day so four is my max number. And two of those are booked. How do I indicate that two out of four are booked, meaning two more are open to be booked? It appears I can only reduce the total amount to two, not indicate that two are taken, leaving two.

OR do they automatically update themselves when they are officially booked and accepted by the owner/sitter?

Thanks!