This was from an old email to Burns:

I found this on the ONSEMI forums:

AX-RadioLAB code sets the RSSIREFERENCE 64 dB (called RSSIOFFSET) higher than the correct value and then subtracts 64 dB when reading out the RSSI value. (And also corrects RSSIABSTHR by 64). This is to prevent wrap around at -128 dBm, since the RSSI register is only 8 bit.

So, it sounds like we're seeing the RSSI as 64dB higher than it really is...