The ranges on the objective lens (or side wheels on some scopes) tend to be different to what you actually get as everyones eyes are different. I occasionally shoot field target and cover over the numbers and re-mark it. Basically, I set targets every 5 yards and when the scope clears mark that on the scope. Its more accurate with higher mag scopes as they will "cut in and out" quicker. But for hunting, I find a good average and leave it at that, don't want to be messing around with the scope when aiming at a bunny!