Thank you very much for your answer.
1. So on the “Main” Surface you would select PreampOnSurface to set global analogue gain and on the other Surface(s)/Editors of the system you would select TrimOnSurface for digital gain in-/decrease for specific needs?
2. Why would an e.g. monitor engineer want a different input level than the FOH engineer?
3. How come the Gain has no meter next to it to set the proper level?
I hope I’m not being annoying – I still don’t get the Trim thing 100% 
