The Binocular's Range estimates the distance to an object based on the range finding reticle (scale) superimposed upon the view. This scale allows the distance to the object to be estimated if the object's height is known (or estimable). The common mariner 7x50 binoculars have these scales with the angle between marks equal to 5 mil. One mil is equivalent to the angle between the top and bottom of an object one meter in height at a distance of 1000 meters.
The following formula is used to estimate the distance to an object: `D=(OH)/(Mil)*1000`, where:
Wikipedia (https://en.wikipedia.org/wiki/Binoculars)