As it is an antitank gun I am going to speculate that you will put the crosshairs using the gradients inside the lense of the scope to make quick corrections to the initial settings from the dials. . The smaller numbers 1-5 may be to estimate the lead for movement of the target, and the larger numbers may be for the distance the target is from you. So for a target that is not moving and 100 meters from you, you will point the center of the crosshair at it. If it is moving fairly quickly, and at 2000 meters, you will use the 5 and 20 crosshair.
I am not familiar with the Russian optics...I just had a look at the 25 pounder manual and the smaller numbers are, in the case of the 25 pounder, a certain amount of minutes of correction and "the graticules allow rapid correction for line being made". The larger numbers are as I indicated for range.
This is just my guess...I am just a collector of this type of stuff...you will be better off asking a gunner.