Two things;
A) Brew Kits are notoriously generous with priming sugar because they assume that people want to drink the beer asap.
B) Following on from point A, if the beer hadn't reached its final gravity and you primed it, with said generous amount of priming sugar, you will find that you have gushers on your hands.
Where as a correctly calculated priming sugar quantity may have only resulted in 1-1.5 more volumes of co2 more than you wanted, of course this depends on the gravity at which it was bottled.
If you were miles away from FG then you're going to get gushers and bottle bombs anyway.
I tend to be more conservative with priming sugar because It takes me a while to mature and drink a batch.
I think that the point to take home from this is to make sure gravity is stable for several days prior to bottling. If it is stable but you suspect that it's higher than it should be then move the Fermenter to a warm place for a week or so and give it a gentle swirl every day. Leaving it longer will do it no harm.
I recently chanced bottling my Wit beer a little early, but only because it's a beer that is meant to be lively, carbonation wise, and is best consumed relatively young. Had it been a different style I'd have left it.
Hope this helps.
