Hahahahahahaha. Indeed!
@shroomie It seems you're really asking (and not trolling). 255 is the largest number you can hold in an unsigned 8-bit integer (“11111111” binary equals 255 decimal), also called a "byte”. So if the internal variable they're using as their member counter for this is an unsigned 8 bit integer, then it can't hold a number larger than 255. And 0-255 is 256 numbers.
(Note: they could be using a larger variable (i.e. with more bits), but only reserved 8 bits of it for this counter).