I recently purchased a Tru-Glow sight thats just as you described.

It took a little adjustment of the sight pin section of the sight to lower it down enough (the lower the better - as it gives you more range of adjustment. When you start working on it you will see what I mean). Then the sight pin range adjustment bar was set as low as it would go and I tested it out at 10 yards. After a little more adjusting I had it set dead on for the 10 yard range. You could probably start at 20 yards - but I was afraid of missing the target and breaking an arrow. Thats why I started at 10 yards.

Then, I put a temporary strip of masking tape over where the blank yardage marking strip is located on the sight (this way I could make a pen mark at each 10 yard increment) in order to get an idea how this sight will finally be set up.

I made a mark on the masking tape strip at 10 yards, moved the range adjustment bar upward a little until I was hitting dead on at 20 yards. I kept doing this while increasing the distance to the target in 10 yard increments, making marks on the masking tape all the way out to 60 yards. I even had enough room on the sight to make a 70 yard mark on the tape.

I had ordered preprinted yardage strips. I found the one that matched up with the marks on the masking tape, and swapped out the masking tape for the preprinted strips.

I had always used multiple pin sights before, so this was something very new to me. Thus far, I'm very glad I made the switch.

I hope this helps.