focus death bug or wtf?

[Discodelic]

   For 2 minutes, decreases user's critical attack rate by 30% and frontal critical damage by 30%. Increases the probability of deadly attack by 60% and rear critical damage by 90%. Requires a dagger.
in rpg x15 it gives 30% dmg ~ so wtf ??

[McCoy]

https://forumen.rpg-club.net/index.php/topic,10861.msg133290.html#msg133290

using search function helps