Can someone explain custom motion zones on 3 plus

I’m about to buy a doorbell 3 plus I think, but I want to make sure this is how it works first as can’t find the answer. My house the garden is about only 1M from front, and the door is on one side. I want to cover this all day with motion, when say someone comes on property but doesn’t push the bell. Can I literally draw around in the app to create a zone that covers my garden only and not the pavement as would get a lot of motion alerts then. Reading, it says zones, looking on videos seems to be selected zones. This would be no good for me.