There are some abilitys where dont stand enough info example >> COMPOUND EYES (or something) there only stands Raises acuracy but when does it raise acuracy? (im not good in spelling)
It just generally raises the Accuracy of your moves by 30%.
So say that a Butterfree (With CompoudEyes) uses Sleep Powder. Instead of it being 75% accurate, it will be 100% since it's been raised by 30% (It would technically be 105% but that's not possible. )
So yeah, that's just how it works. And now that it's answered it can be closed.