16 bit = 48 bit their both the same thing represented in a different way.
e.g 1 pixel is 48 bit in total, but obviously there are 3 colour channels (red, green and blue) which each represent 16 bit and 3x16 = 48.
(This explanation might not be quite accurate, but its the best way I can think to explain it).
EDIT: abdoujaparov beet me to it.