Ruling energy root question

[rkomarco]

let's say a infernape has a energy root, his maximum hp goes from 100 to 120.

let's say he has 10 damage counters on him, who would be enough to ko a normal infernape, if i use a windstorm and discard the energy root it's hp comes from 120 t0 100 and since it has 10 damage counters would he be knocked out?

please answer

 

[Chairman Kaga]

You have it right.

The instant the accumulated damage is greater than or equal to the Pokemon's HP, the Pokemon is Knocked Out.