I just got a new Leupold VX-III, and have been going through the owners book trying to figure out all of the bells and whistles... I dont completely understand the range estimating section. I understand how it says about from the breastbone to the back being 16 inches, and lining that up with the bottom of the reticle to the middle. But how that corresponds to the number on the magnification ring is baffling me. can someone help?