Originally Posted by sveg
I have never seen other limits than 4 and 9, so if you see another number, for example 3 or 7, this should mean exactly 3 or 7 seats available in the bucket.
Actually, 7 is a maximum used by some airlines. But it's often easy to spot when that's the case, because you'll just see a whole line of 7s - just like seeing a whole line of 9s or 4s.