Hi: The key has no stop, that's to say it is just pushed until the lock opens. That means the relative bit depths are important and the absolute depths do not matter. For example a lock with two wafers could have 36 possible keys if there was an absolute reference, like in a pin tumbler. Bot for a lever lock with two wafers there are only 11 unique keys (fewer of you can flip the key over). I have not figured out a general formula, got the 11 by listing all of them.
http://www.prc68.com/I/Locks.html#Lever_Pancake_Padlock

Have Fun, Brooke