I have question about output level in Fireface 400 Audio Interface.
According to user manual it is said that I can set outputs to: -10 dBV, +4 dBu and Hi Gain.

Let say I set phone output to +4 dBu.
What does it mean from user manual: "Output level at 0 dBFS @ +4 dBu: +13 dBu"

For me +13 dBu is 3.45 V (RMS) or 9.79 V (PP)
Suppose my software is generating sine wave peaking exactly at 0 dBFS. How should I set volume fader (position ) in FF400 to measure this 3.45 V (RMS). Is this position 00 for PH output in +4 dBu mode?

And the same question according the above is right. Should I set -13 dB in TotalMix for Phones to measure +4dBu at the phones output (1.23 V RMS)?