I have set mine (if i can think without plugging in) 10.75 and 10.00
I noticed that I got the warning light and landed and by the time i got home and plugged the battery in to recharge, the voltage had removed a bit from the set warning voltage and was at 11.4.
So I think the quad is measuring battery voltage+prestent load, and as soon as it touches 11.2 the warning initiates. If that is the case, all that needs to be worked out is a safe auto amount of voltage to get it on the ground before reaching 9.6v.
The warning can go off anywhere you decide before. So if fly low as you really need to be to see it during day flight, does need to be set that much higher than autoland.
At altitude or FPV you are not going to see it anyway.
Just need to sort a safe landing and work out how much voltage is need from say, 400m or so.