On the 05-06 ZX6R, if you push that switch to the left, it will start the lap timer. In order to see this, you have to change the mode on your instrument display to the lap timer mode. The lap button that is on the left is what you push after you complete a lap. It keeps track of how many laps you have made. I'm guessing all of this works the same way on the zx10. Hope this helps...