Is Charizard EX Burning Darkness damage calculation broken ?

So reading the card attack description is states

Burning Darkness

180+

This attack does 30 more damage for each Prize card your opponent has taken.

So reading that it makes sense to me that if your opponent hasn’t taken any prize cards the attack should be only 180 hit points correct ?

I’ve had multiple times today where the attack doubled or tripled without me taking any prize cards .