It seems that I’ve got your idea now!
You need to let only 1 booking per time slot, but since all services share the same schedule the slot disappears from all services (spots) after 1 client booked it.
If everything is correct, unfortunately, it’s impossible to implement this idea now, since individual schedules for each service aren’t supported now. However, this idea is already on the Wishlist and you can upvote it here - Be able to set different schedules for each service.
If the idea gets more votes, we’ll try to consider it in the future updates 