Understanding the playback meter

[Becherovka]

I'm really loving my new Ultra and am busy exploring all of its features. I have set the playback screen to display the meter and I'm wondering what the displayed db value represents. Does 0 correspond with the maximum output voltage of the Ultra's analog output (2.1 v RMS per the specs) or 0 dbfs for a digital output? I ask because I am wondering if I can use the meter value in combination with the db gain of my PA to calculate the power being output by my PA.

 

[hgo58]

See the other threads about the VU meter. E.g. "VU meter".