I have an EPMP AP at 5770/20mhz on latest firmware. I have four SMs (all integrated) connected to it, also on the latest fw. I have the power levels on all four set to manual. I have each one set to Output power 21 and antenna gain set to 14. However, on the home screen of each one, I get a different reading for one radio. Two are at 21/15, while the other one is at 18/15, (one is offline right now).
I can assume every SM has unique Wireless conditions and ATPC set Tx Power on each one to get same UL RSSI on AP. Please check my hypothesis (Attach Monitor Wireless page from AP).