Your Vortex second focal plane (SFP) reticle with MOA subtensions has a cross hair that centers the sights on target. According to the manual, each of the hashmarks along the verticle and horizontal crosshairs of your scope represents 2 MOA (roughly two inches *) at 100 yards using the 16x setting. So the distance between the centers of adjacent hashmark represent 2 inches at 100 yards, 4 inches at 200 yards, six inches at 300 yards, etc. Hashmakrs on the horizontal crosshair line provide windage information and those of the vertical line provide information on elevation. If your scope is sighted with a 100 yard zero (point of impact on target matching the placement of the center of cross hairs) and, using the same cross hair centered sight picture, at 200 yards the bullet hits the target at a point corresponding with the hashmark directly above the horizontal line of the reticle, you can judge that to be 4 inches high at that 200 yards distance.
(*) The actual measurement for 1 MOA is 1.05 inches (2 MOA 2.10 inches) but you can't begin to maintain a hold on target within that level of tolerance so don't worry about the .05 inch ....
A pronghorn antelope will measure approximately 15 inches from the top of the back to the bottom of the chest. If you put the center cross hair of your scope on the back of that antelope and the second hashmark below the horizontal cross hair aligns with the chest you know that the anetlope is approximately 375 yards away. (15/4 = 3.75 )