It's one of those things. You'll probably find that the computer mainly serves as a communication point to an even larger computer on Earth.
It's like the story about Apollo 11 having the computing power of a washing machine, but the truth is the computers back on Earth driving it were some of the most powerful on Earth at the time (apparently about the same spec as a modern day laptop, although I find this claim dubious). The computer as powerful as a washing machine primarily communicated with computer the power of a laptop.
I imagine NASA, in a bid to reduce payload or whatever, have all the bulky powerful energy hungry computers here on Earth and just use the computer on the space shuttle to communicate the processes of these Earth based computers to it.
