Your probably wondering the same thing I wondered when I first looked at those. There isnt a seperate scope for each caliber it is one scope with basically a bulet drop compensation for each caliber. For any given caliber each line represents the yardage then you have to basically figure in a correction for the bullet drop. Maybe it would just be easier this way I will put a link up. Check out table 1 that gives you the breakdown for each caliber and type of bullet.Hope this helps.
http://www.clcweb.net/Shooting/Coope...lex_scope.html