As with many measurements, a value in specification confirms to a certain extent the validity of this part of the door system. An unexpected inclination can point to different causes. One could be that the vehicle with the observed characteristics was not sitting on a level ground. Maybe, in case of active suspension or load case, the vehicle was tilted. When the test is expanded to left and right, we could look for symmetry or asymmetry. Asymmetry could point in the direction of a squareness issue. Unrelated numbers could simply point to an issue on the hinge installation on one side. All assist in troubleshooting and identifying the right cause.