Not sure what #'s you are referring to, but here is a little general info.
Ex: A 3-9 x 40 scope is a popular size for all around use and would be good on a muzzleloader. 3-9 refers to the magnification range of the scope...adjustable from 3x's mag to 9x's mag. This magnification can be adjusted by a dial on the end you look into and should not affect the zero of the scope.
The 40 refers to the size of the objective lens (exit end of scope)and is measured in mm's. The larger the objective, the larger your field of view (FOV) when looking at distances.
Joe