The aim of the game is to have the target & the crosshairs at the same plane of focus. If the crosshairs move across the target when you move your head up & down or side to side, then they aren't coinciding - assuming that your rifle is solidly rested & you aren't bumping anything around when you move your head about.
However, before all that happens, you need to get your scope crosshairs focussed to your eye while you have relaxed vision. This is a real bugger with Leupold VX -IIIs because the socalled quick focussing adjustment is far too slow & your (my) eyes quickly accommodate to focus on the crosshair - the exact reverse of what should happen.
I was told that one trick to use is to crank the focussing bell back as far as it will go then crank it in half a turn at a time while you're looking at a neutral background (as the book tells you). When you see the crosshairs sharply, stick a piece of masking tape on the bell & put a pencil mark on it at exactly 12 o'clock. Ten continue winding in half a turn at a time, keeping count of exactly how many turns you make until the crosshairs go out of focus again.
When that happens, back the lens out exactly half that distance & as the story goes, that's your best focus for the crosshairs. In my case, I usually end up doing it several times, thanks to that stoopid slow adjustment.
crosshairs or target move?