Um, you're referring to the DECIMAL form of subnet addresses (re: 255.255.255.0), it is *NOT* base 256, it is base 10. It is the decimal format of a binary number. If it was base 256 it would have two possible values, 0 and 1, 0 being 0 and 1 being 256.

It scares me that you're teaching other people subnetting :/