if you have one at 1150mah, try a discharge and see if it improves.
I have one of these chargers, and was also surprised how different the actual mah figures were from the manufacturers.
Not only that, every recharge will give you a different figure, sometimes good sometimes not so. I even have some that exceed the quoted ratings.
Generally if they give a poor rating after top-up, I use discharge mode, which automatically recharges when finished. Things normally improve after this, but sometimes I'll need to repeat. Or use 'Refresh' mode, but yes it'll take a while.
agree with above – manufacturers quoted figures may well be a bit optimistic.