Installing SRAM caliper brakes
 

I'm assembling a road bike from components for the first time. SRAM Red groupset, carbon frame and fork. The brakes come with a washer on the caliper bolt. It has a knurled outer circumference and and is a slip fit on the caliper bolt thread, meaning that it is sloppy on the non threaded part of the caliper bolt. Since it won't fit inside the hole on the non-caliper side of the fork, the only place it can go is between the caliper and the fork. I've installed it that way, but it doesn't seem right to have a sloppy washer in that position. Can anyone tell me why it's there, what it's supposed to contribute?