Android, the difference between the level and RSSI of a Wi-Fi signal?

I really don't know much about radio / WiFi signals, so am I confused by the difference between the WifiManager.ScanResult level field and the wifi scan RSSI ? Are they completely different concepts? Both of these do not seem well explained in the Android Docs.

Both of them seem to be in dBm if that means anything.

EDIT

To be more clear, I'm talking about the value returned when searching for the WifiManager.EXTRA_NEW_RSSI key. This is explained in the document: WifiManager.EXTRA_NEW_RSSI: The lookup key for an int giving the new RSSI in dBm.