5.11 skins reward for challenge

Hello, I have baught 5.11 skin pack last week and after this week update i noticed it gives you for completing some kind of challenge. Can not find those challanges in menu. Is it some kind a bug that I see it or is it really a reward for something? If so I think it is a bit unfair for those who baught it, I think 1800 battlefield coins completely wasted...