Perhaps this will help understand how to "forget" inches.
-Assume you are zeroing your rifle at 200 yards and you aim at the bullseye and the bullet is low halfway down the target.
-Put your scope back on the bull's eye and look at your reticle to determine how many mils low it is using the scale of the reticle.
-If it's 2.5 mils low, dial 2.5 Mils UP. Who cares how many inches it is.
-Done.
If your scope is FFP, It doesn't matter if you performed this at 200 yards, 50 yards or 500 yd it will still work at any magnification. If it's SFP, it'll only work like this on a single preset magnification level (usually max magnification)
