Not sure what you mean by that. I'll take a stab though. On that unit point the "blue" arrow at your target. Then spin the blue ring until the red arrow in it is inline w/ the red "magnetic North "arrow. At this point your heading is the number on the blue ring that is below the blue arrow.
Yep, I figured I usually have a compass on western hunts so one day I was thinking about it and came to the conclusion I can lay the compass on it's edge place it on the barrel, scope tube, ect as the gun points at the target. have the compass zeroed out and the little buble floats to the top and you read the degrees that the buble indicates.