I'm confused on the Team Fortress test how did the Radeon HD 4870 get a higher frame rate (91fps) then the Radeon HD 4870 X2 CrossFire (86fps)??

THIS GAME IS AMAZING AND PLAYS VERY WELL ON MID-HIGH SETTINGS,(LIKE I KNOW IT SHOULD) WITH MY 8600GTS AND A RESOULTION OF 1280/1024