I have the TLR75 view thru right eye and my thumb wheel is on my left. Mine is a split image and as i go to right yardage they come together as one. read yardage and thats it! On bottom of mine it has a calib.button and a Vertical image correction screw. I pick out an object i know to be 30-70 yards and focus, if its out of calib. leave it at the yardage it said. Push in calib.button and hold it in while you turn yardage wheel to the correct yards and thats sets it for being calibrated. Hope this will help you.