It rotates way more then a few degrees. I didn't have the tool for it so I just spanned the center circle with a pair of pliers jammed in the slots, I put a lot of pressure on the pliers and twisted, it worked to rotate the piston back.
I don't remember how many turns I rotated it, I just keep going until it stopped rotating. It could take a few complete turns. Just make sure to line up one of the grooves/valleys of the "+" with the center, you will see a small tab sticking out on the pads, this has to go in the valley for the pads to sit flat. So you can rotate the piston as far back as necessary as long as you align the "+" correctly for the pad.
Keep in mind as you rotate you are moving the parking brake back, so when you finish and get back in the car, BEFORE you drop it off the stands, pull the brake lever a few times to cinch the brake back down. The first couple times you pull the handle it will be very loose and offer no braking force. After a couple of pulls and you should feel it returning to the normal parking brake engagement force.
Also if you got that far you beat me! On my first brake job I spent 20 minutes trying to figure out why the darn pads and rotor were stuck before I realized I left the parking brake on! [

~][rofl]