Assuming it´s a second focal plane reticle, you need to check the scope manual.- or ask the dealer or manufacturer. Sometimes it´s the highest mag, sometimes in the middle if it is a high powered scope.
The best thing to do is mark off a 100 yards and stick a piece of pvc in the ground with electricians tape or ?? marking off 36" (3.6"X10 mils) and see where the actual setting of power is on the scope and mark it (scratch??). The 36" marks should line up exactly at 10 mils. The scopes often are "off" at the factory setting.