AOB will not be messed up if you use the wrong magnification setting, either by ingame choice or camera settings. The AOB calculation is basically to compare:
1. Known relation between real height and real length of target. (nothing short of torpedoes can change this relation
)
2. Relation between observed height and observed length of target, which is also unaffected by magnification.
Range will be wrong if some other magnification is used and no correction for that is made, but not AOB as long as everything else is done correctly.