Ring doorbell misses letterbox

I'm new to the Ring doorbell 2nd generation. It frequently captures people walking past the house. However whenever anyone delivers a leaflet or the postman posts theough the letterbox, this motion isn't detected. The doorbell fitted to the frame on the right of the door. The letterbox is in the middle of the front door. Not much of a slope or steps up. Just one step and then step up and over the threshold. A short driveway. I cannot figure out how to angle the camera from the app. Do I need the corner wedge kit? It seems to defeat the object im aware whenever someone passes by but doesnt detect certain important movement actually at the front door.