I am having a hard time understanding what the numbers mean on ROM. If the number is over the average does that mean that muscle could be overly stretched and you would have to strengthen that muscle and possibly the antagonistic muscles?
ROM means the joint has natural ROM. It implies that the joint is freely moving with the antagonist muscles cooperating equally. The muscles doing the motion are not contracting during ROM test. The joint is moved passively so you cannot test the muscles from this test, only assess the joint.
If the number is less than the average does that mean that the muscle is tight and or the antagonistic muscle is tight or week? Then you would MT those muscles.
If the ROM is less, then the antagonist muscles are tight. For example if you text external hip rotation and get a reading of 30 degrees instead of normal 50, then the internal hip rotator muscles are tight on that side. If the ROM is greater than normal ROM I would test both antagonists to see if either is weak.