Offizieller Kommentar
I'm not sure of the calibration value of the XDJ-XZ, but I'll say the same thing I tell anyone asking about this... use your ears and compare the meter readings on the devices that count. If you're recording, look at how the recording levels are compared to what the meters show on the DJM or XDJ itself. If the output recording was a decent -6dB peak (as measured in software after recording) when the channel meters were peaking at +3, then that's where you aim for next time.
