In GT2, Bound is supposed to mean the shock absorber is compressing, ie-getting shorter. Rebound is when the shocks are extending, ie-getting longer.
According to the manual, the higher your Bound number-the more resistance the shock has towards full compression and the higher the Rebound number-the faster the shock absorber will extend.
I've seen some folks on the net disagree--they think that higher damper numbers mean the shocks are weaker...