It's probably set to sync the frame rate to screen refresh rate. LCDs have a technical refresh rate of 60 Hz (they don't have real refresh rate in the sense the CRTs have, but they have to report something. It's usually a checkbox somewhere that you might uncheck.
Note that this only affects the number in the counter - it still won't draw more than 60 frames per second to the screen, but then neither does any other game.