7/8" Weaver is the width of the dovetail.

1" is the diameter of the barrel (narrowest tube of) scope.

dovetails for .22 (caliber) guns are 3/8" wide.

Horton bows have always used 7/8" Weaver dovetails and their all their scopes take 1" diameter rings. This follows the standards for most all scopes and rings used in the gun industry.

High Med and Low are the distance from the dovetail to the centerline of the scope. This allows you to move the scope up or down slightly to get a better sight picture when mounting the gun.