My fiber line is 500/50 (down/up) and although i have connected the RE315 a few centimeters away from the Fritzbox 7530 as a repeater, i get 220/50 from the RE315 !!! 

RE315 supports 867Mbps out of the box??

I have updated the RE315 to the latest firmware but still the speed is the half regarding the routers download speed (sad) BUT the upload speed of RE315 is 50MBPS = the router upload speed!! why??