I have a leupold with the B&C reticle and a Swarovski with the TDS reticle both are compensators for bullet drop. They explain how they work when you get the scope, but some bullets/loads work better than others.

In my .270 I shoot 130gr bullets
my .300 win mag 180gr bullets
my .340wby, 225 gr line up perfectly with the drop, 200 and 250 work well but not dead on, thats why i should premium 225 gr through it, at 600yds, that elk is dropping!

Figure out the drops of each crosshair, then go online and look at ballistics and figure out a few loads that are suppose to be really close to those drops.