Cof index is a system to prevent people from "rapidly upgrading" in the game. This system can prevent big players from upgrading directly with small players. Generally speaking, the higher the cof index, the worse it is for players.

DNFcof reduction method:

First of all, we shouldn't team up with players bigger than our own Lv7, which often leads to a consequence. At that time, when we upgraded, every time we entered a dungeon copy, we would add a little cof；; Cof value is difficult to eliminate;

Brushing your own map can effectively reduce the COF value, and upgrading can also reduce the COF.