AD9371 ADC Full Scale not reached

Below is a plot of input power (dBm) of a CW signal slightly offset in frequency from the Rx frequency versus the actual AD9371 magnitude of the I and Q codewords.  The recommended max RF input is -14 dBm for which I would have expected a full scale output of 2^15 for a 16 bit ADC.  The ADC also looks like its being limited.