Epic Jewelry Bonus

Epic Jewelry Bonus - Bonus from the worn Epic Jewelry.

The jewelry description gives it in %, but don't forget that it's added on top, i.e. +4% is 104% when multiplying.
Example: +4% P. Atk in Necklace of Valakas is counted by the game as the number 1.04 in formulas.
Effects from two identical rings or earrings don't stack. If more than one piece of jewelry gives the same effect, it must first be summed before being used in a formula.
Example: Ring of Queen Ant and Ring of Baium both give +30% Crit. Dmg. - so the formula will use the number 1.60

You can read about the bonuses themselves on the Epic Jewelry page