I fill my diffs until the oil starts leaking out of the fill hole. The manual for my car says that 'full' is 5mm (or so) below the fill hole, which is impossible to accurately do. So filling until overflow and then allowing the excess to drain out is good enough.
I'd wager that you didn't actually add the necessary 1.92 quarts, as there is usually significant residual gear oil that's hard to get out of those bottles. But you're probably close enough, so I don't think that this is a significant issue, but I'd top it off just to be on the safe side.