The scope’s ocular ring has engravings representing speeds from 275 fps - 425 fps and magnification from 2x – 7x. To program, simply mount the scope on the rail of the crossbow using high-quality rings, then set a target at 10 yards using the 20 yard (1st crosshair from the top) and shoot until you hit center, then repeat at 20 yards. Once the main 20 yard reticle is sighted in, turn the speed indicator on the ocular to the manufacturers advertised speed (this may vary based on bolt length and weight). Now move the target to 30 yards and sight in using the 30 yard reticle (2nd crosshair from the top). Once the 30 yard crosshair is sighted in, the scope is now calibrated to your crossbow and all of the other aiming points will be correct. Crossbows with speeds over 425 fps and using a lighter arrow combination may require a main crosswire sight-in point of 30 yards instead of the normal 20 yards. This will require calibrating the scope at 40 yards to compensate for the flat trajectory of the crossbow bolt. The owner’s manual includes more detailed setup instructions.