Mew's Genome Hacking dosen't behave properly with Togekiss' Overdrive Smash

Poptarts4Sale

Using Genome Hacking on Togekiss twice in a row displays the special tag of Overdrive Smash doing more damage next turn but only does the base 60 again. The ability text is as follows: During your next turn, this Pokémon’s attack does +60 damage. I would assume it would do 120 damage the second time but maybe my understanding is wrong.