there is a Pin on the heat sink and a notch on the bracket. the two will line up when it is correct. the pic does not show WHY the change is needed but this is the reason. if you look at the pic the bracket is in a different position. look real close and you can see the top arm is in a different spot.
EDIT when you look at the physical bracket and open it the confusion will be understood because the design of the bracket. if you only open it a notch it will fit one socket then open it one more it will fit a different socket and again the third notch will fit a different bracket. just take your time and don't rush. I'm an ex mechanic and it took a few mins to figure out mine for my AMD setup. match the bracket to the pick And dry fit it first.