Asus m4n82 mb sli config slot placement and mhz profile

Hi and thanks in advance to anyone who can help me. I have dual nvidia graphics cards in sli in an asus m4n82 mb. cards in pci e slots 1 and 3 for 2 x 16 configuration. According to the manual those are the right slots to use. When I check my nvidia performance monitor pci e slots 1 and 2 are reading 5,000 mhz and slot 3 is 37,500 mhz my experience with reading and interpreting what this means is limited. It just seems like something isn`t right. Almost like it may only be recognizing one card or that the reading is way too high. physx enabled also. Thanks again.