Can you overbook availability slots?

Hello! I am a new sitter and I am trying to figure out how the availability slots work.

I have two repeating daily walks. But when I check my availability in my calendar they do not show up until the new week starts.

Right now I accept 3 walks a day, but will need to go to two once school starts. I want to block those two walks out so people don’t try and book me if I am technically already full.

If I were to subtract two walks from my daily availability would it effect the repeating walks?