I'm not sure, but last I knew Burris wasn't in the xbow scope business. I mention this because if not designed for xbow use, that might be your problem. Like what's already been said, most xbow scopes additional aim points are for approx 10 yd increments.

I'd be interested in the model of your scope. I know Danny Miller, USA warranty rep for Excal sells a version of Leupolds shot gun scopes that uses the top duplex, crosshair and bottom duplex to get 3 ranges, all 10 yds more. By 'duplex' I mean where they thin down.