Board Thread:General Discussion and Questions/@comment-28424239-20160522000351/@comment-27904998-20160523023006

You probably have 100% already. If it says "Congratulations! You've completed every stage of the achievement." then you're done. Even once you're done, it will continue counting the number of artifacts you've assembled.

I use the More the Merrier achievement to see how many friends I have. 😛