Hi Chris,
When it comes to digital desks, there are some things to consider with meters and faders and outputs.
The following article is a quick read that explains the different types of metering being used (https://www.audiorecording.me/what-is-the-difference-between-dbfs-vu-and-dbu-in-audio-recordings.html).
Unity, or 0dB gain at the fader, just means you are not affecting the level with the fader position.
But if an output meter is at 0dB, the output socket is providing +4dBu.
Also, USB outputs on the Qu are digital, so users often think they have a low level.
More info here – (https://support.allen-heath.com/Knowledgebase/Article/View/1121/201/-18dbfs-and-metering-in-qu-and-your-daw).
I’m sure others will chime in with helpful advice too.
Cheers,
Keith.