How does the oscilloscope calculate the distance?

How the range calculates the distance;

There is also a crosshair between the objective and eyepiece of the sight, which has a crosshair as thin as a hair crossing each other (so it is also called "crosshair"), which can effectively assist the sniper in aiming, such as measuring the distance (taking the SVD sniper rifle as an example, the lower left corner of its PSO- 1 sight has an arc from lower left to upper right and a reference horizontal line, and the upper left corner of the arc has a number "/kloc-0". If it is assumed that the lower edge of the foot of a standing target with a height of 1.7m is cut on the reference horizontal line, and its head coincides with the lower edge of the arc, the number of arcs is compared. If it is 4,