Divisible by 25

Noticed something odd this morning. In my experience, hero point awards are gained and spent in numbers divisible by 25. Somehow, I currently have 485 hero points. This may be silly, but can anyone explain how that happened?

if you were 11-20 in the boss battle you got 10 hp do not ask me why as it is essentially useless. also if you buy during a sale I think the 30% on some of them break the divisible by 25 thing

Thanks! Now I can stop scratching my head about it.

I can confirm that the 30% sale is what did it to me.