On the 5.0 exam you don't need to worry about this stuff at all.
On the 1.4 exam understanding bit repesentations is a minor topic, and mostly you need to understand two-s complement and binary representaions in general, so that you know a big number, or a small number, or a negative number, when you see one. You don't have to be able to calculate 2^N where N is say bigger than maybe 4