Firing sniper rifles

Unlike OFP, Sniper rifles in armA don't seem to have range adjustments. The target sights of the M24 are ranged for (1000?) metres. To hit soldiers closer than that, you don't use the centre of the cross hairs, but need to use one of the notches above the center cross hair.

1 notch up: Distance = ? 2 notches up: Distance = ?

(A picture of the sights would be good here)