Choice Band & Tapu Koko

[gamersgambitct]

If a Choice Band is attached to a Tapu Koko (Sun & Moon promo), how much damage will Flying Flip deal to the opponent's active Pokémon-GX or -EX? Assume no weakness or resistance.
Flying Flip
This attack does 20 damage to each of your opponent's Pokémon. (Don't apply Weakness and Resistance for Benched Pokémon.)

Choice Band
The attacks of the Pokémon this card is attached to do 30 more damage to your opponent's Active Pokémon-GX or Active Pokémon-EX (before applying Weakness and Resistance).

 

[PokePop]

It will do the extra 30 damage.
It doesn't matter if damage is done from the big number to the right of the attack name or from damage calculations described in the attack text; it is all still damage.
The only time you don't consider it damage is if it is "damage counters" which use quantities of 1, 2, 3, etc instead of 10, 20, 30, etc.