I am studying for the CompTIA Network+ exam and have a question about subnetting. The example given is that a cafe requires 3 different networks. One for guests, one for employees and another for wireless. The formula for determining how many subnets you create is 2^y. In this case, we want to create 3 therefore, 2^2 which is 4. So why is it that in a subnet of 255.255.255.0, you only go back two bits vice 4? I can't help but think that there is some common knowledge here that I am missing.