WOIN WOIN How does the Push weapon special quality work?

One of our players has a Bell Cybernetics RVM58Stingbolt Repulsor Crossbow (Exotic Ranged Weapon from NEW pg. 106) with the Push special quality. I can't seem to find how to resolve the Push ability. Is the distance based on the attack roll or the damage roll or a flat distance? Is it an attack against Vital Def instead of Ranged?

Page 167 of NEW you have all the called shots and one of them is to move the target which includes Melee and Ranged.

"Make a Called Shot with a melee or ranged attack and if you hit you move your target one square (plus up to one square for each size category by which you exceed the target in melee, or by which your weapon exceeds the target at range). You must pay an additional 1d6 for each size category that the target is larger than you, and also if the target has more than two legs or has no legs. The movement must be one which makes sense, and if it is a result of a blow or ranged attack, will always be a push away from you."

I assume the Push trait is the same as the called shot without the dice penalty. Hope this answers your question