cast on/off adjustments

[hofts]

i have never ever done any adjusting on my shotguns, however tonight in the house i was putting my cordoba up to my shoulder quite a few times and i noticed that my shooting eye was lined up to the left of the rib a lot of the time. not straight down the pipe.

does this mean i should maybe adjust cast one way or the other, which way??? i am right=handed. do the adjustable shims that come with benellis do any good? the instructions seem to be a bit hard to understand for cast on off measurements. any input would be appreciated, thanks
jj