Ignore zone is not wide enough to ignore car wheels being detected as humans

The motion detection constantly detects parked car wheels as humans on my video doorbell. I have used the ignore zone configuration to cover the area where the wheels appear, but the zone does not allow me to make it wide enough to ignore the full range of car wheels on the street. The result is that if I cover one area where cars are parked, the area either in front or behind begins detecting humans for the wheels. I cannot make the zone wide enough. Why is there a restriction as to the width?