What does this rule mean?

7.5.5 No body component with the exception of the radiator air deflector shall be lower than 4” measured vertically from the ground. Radiator air deflectors shall be no more than a total of 6 inches wider than the radiator itself and no lower than 2 inches measured vertically from the ground.
Is it 4 inches from the ground or 2 inches from the ground?

I am making a ride height adjustment and want to make sure my air deflector is not too low afterwards.

Also... Where is ride height checked on our cars? It is 4.5 inches from the ground.