each groupset rises in numbers but starts with the same number so.....105, 5500, 5600, 5700. ultegra (which used to be shimano 600 and tricolour) 6500, 6600, 6700. dura ace, 7500, 7600, 7700. every time there is a new release of the same product the 2nd number jumps up by 1.
the 2200 stuff is shite, I know this because I had it. its budget shite. I replaced the calipers for 6500 ones when I needed new pads and got a pair of nearly new calipers with new pads from the bay for 28 quid. thats a fiver more if I had just bought the pads/blocks/shoes whatever you want to call them.