Briefly, playback signal in Totalmix reports -22 dBfs and Digicheck reports -15 dBfs on the same output/ playback channels with channel faders at unity?

I have a UFX+ connected via MADI 648 to Apogee 16X via ADAT. The DAC has a conversion level of -16 dBfs equals 0 dBVU. I am sending a -16 dBfs test signal out of Pro Tools  Signal to DAC is going out through the Apogee.

What is going on?

Thanks