I checked the manuals and forums for the Focals, they have not stated in detail regarding the +4 and -10 settings. But, when I set it to -10 dBv, the sound is much more louder and more details can be heard with lower output levels on the Babyface.

For example, I just changed the setting to -10dBv and played the same music at -12 output level on TotalMix and the RMS level peaks at -26 dB but generally is between -30 and -46 dB on TotalMix but the speakers sound much louder, as if the speakers are being driven super hot, sounds like PA level loud.

This is something the Focal Tech wrote on Gearslutz when someone asked a similar question, don't know if it helps?

"It seems a lot of people are intrigued on the +4 / -10 settings on Focals. I know this discussion is mainly centered around Twins, but every Focals have similar input gains.

Short answer : use +4 with +4 sources.

As you may have noticed, Focals, when compared side by side to other brands, at same volume, have less sound output. That's because most monitors at +4 have actually way too much gain! (you quickly realize that when your monitors are playing insanely loud and yet, you're not even halfway on your volume control!)

We're doing this for a couple of reasons. One of the main reason is that by having lower input gain, you can use the entire volume control effectively.

By doing that, chances are that you'll be monitoring at a volume position higher than 12 o'clock, which reduces signal to noise ratio (most consoles or monitor controllers use regular pots which do sound better at higher volume)

Still, you should be able to crank your Focals to really really loud levels anyway (as some have noticed, Twins in particular can reach PA-like levels pretty easily!"

I have contacted the Focal Support regarding the same too. But any help with your knowledge would be truly appreciated.

Thank you Matthias!