Hi, Timo 

The only ways how you can limit the number of bookings for a service is either if you set working hours of the assigned employee accordingly;

or if you set Time Off for the employee;

Also, if the employee is synchronized with a Calendar, you could create manual busy slots in the calendar, and that will be blocked times in Amelia.

Also, for Group bookings, you have to set the minimum/maximum capacity how many customers can book same time slots.

But other than that, we don't have other ways, at this time.

Can you elaborate on this with a bit more details, perhaps i did not understand exactly what you meant to achieve?