I think this is the key. I have the 4* Magicites that I got from completing all the 3* dungeons (the 2 duplicates from each element at level 99).
Looking at that chart I can see the Elementa 15 gives 15% bonus and drops sharply for a second one. But I'm super confused as to the attack ones. ATK 20, on someone with no buffs gives 71% increase in damage if their attack is 570? Is that how I'm supposed to read that?
Also what do the actual magicite combined stats do?