The amount of overlay is determined by how much the door goes past the cabinet box opening. For example, a 20” opening that uses a door that is 21” wide, overlays the opening by ½” on each side.
The overlay amount you want is entirely up to you, we do not add any overlay amount to an order that has been placed, we assume everything that is entered is a final door measurement with the overlay added in.
1/2" overlay is fairly standard, so if you are not sure what overlay to go with, that is a good place to start.
If you have any questions at all, please feel free to contact us.