John
Never ever adjust the fader in Sonar when recording. It has no effect on the incoming signal but may give one a false reading if it is adjusted. It is only the hardware that has control of an incoming signal in Sonar. This is very important. 

Duly noted.
I should have said that more clearly as well ... thats why I keep them below just to get a signal, there's never a need adjust anything this side of the i/o when recording anyway until monitor stage.
I want the cleanest signal coming in, not the loudest .... but I didn't think about false reading etc.
Thanks John

Now I am more confused. If it is in the wrong place (too hot), start over? Or are you saying as long as I can hear myself in the monitor,  and my "2i2 "halo" is green, I'm good to go?

If its too hot it could clip. When recording stay in the green. Hitting the yellow is OK but never let it clip. 

charlyg
Now I am more confused. If it is in the wrong place (too hot), start over? Or are you saying as long as I can hear myself in the monitor,  and my "2i2 "halo" is green, I'm good to go?

"Clipping" means the signal is too strong and is distorting, so keep the 212 in the high-end of the green, and as long as you can hear it you're good to go yes.
 

if you clip digital, you'll know it.  record at 24 bits and record peaking at -12 db to -6 (in the sonar meters) and you shouldn't have any problems.