Yea. X is the unit all measurements are relative to. X could mean something like 7,600 spins per second or something. But to make things simple, they've taken some constant as the unit and then displayed all drive speeds as a multiple of that constant.
My laptop drive is 4X. =/
56X is fast enough. Years ago I remember reading articles that it was too fast - too hot or something. I'd assume such issues are resolved now.