CC2540: RSSI vs 'Received Power'; TI Composition of RSSI ?

Part Number:CC2540

Is anyone aware of an 'Application Note' or other documentation of exactly how the RSSI values reported by CC2540MA are constructed ?   Do they relate directly to specific dB values seen at the receiver ?   Are the RSSI values just the 'received power at receiver' adjusted by the Transmit Power contained in the advertisement message from the Bluetooth beacon ?    Is there some difference between the reported RSSI value and measured power at the receiver ?

Please advise if you can.

Thanks in advance.