Originally Posted by
Danvash
If you made this thread just to brag, then congrats.
The answer is that, as of Legion, hidden tracking achievements are added to the total number but not to the number you've attained, so you can never truly see 100% until they revert that change.
Hidden achievements can only be seen through data mining and add-ons, and they are awarded when your character unlocks something so that the game has something simple to check for. For example, when you reach artifact knowledge 50, you will get a hidden achievement that will tell the game to stop allowing you to research any more.