INFO ABOUT HIDDEN ABILITY

[Atmosphaera]

When there are a pokemon without hidden ability (for example zekrom), in pkhex there is a window with the same ability (in this case teravolt) wit (1) - (2) - (H). Now if i put tevaolt (H) it become not legaly but in game nothing change. So why there is this difference on pokemon with only 1 ability?

What happen if i put teraolt (H) on zekrom?
Thanks in advance

[theSLAYER]

Think of it this way: in the personal_info (the game info in the ROM), this is what is written for Zekrom
Teravolt (1), Teravolt (2), Teravolt (HA).

It's important to note ability number is part of the Pokemom data structure.
So while the ability is all Teravolt (and it would show up in game), the ability number is incorrect, hence why PKHeX flags it as illegal.