32 bit/channel is a bit different in that it does extend the range so each value can be darker than the darkest displayed black or whiter than the whitest displayed white. That does not give a larger range, just a larger number of steps across the same range. So in 8 bits/channel there are 256 possible values. The bit depth 8 bit 16 bit or 32 bits/channel is the number of bits used to store each value. In CMYK it is one for Cyan, one for Magenta one for Yellow and one for Black. In the case of RGB it is a value for Red, one for Green and one for Blue. The colour mode - RGB or CMYK describes how the colour is stored for each pixel.
