I can tell you that is the fact, that the buffs stack on the current Value of Stats. But this is correct in c3. Its just a problem when you add costumized things in. Like Special M.Atk Weapon which increases M atk by 45%%%%%%% and not just 45 M.Atk (which is the usual way) Or Now changing the Atk Speed Tattoo but let the Casting Speed tattoo untouched.