Thread:Anythingspossibleforapossible/@comment-28070587-20170617213251/@comment-252417-20170617213719

It means to "To be added". It's distinguished from "None known" because more than likely something could be added to trivia, while all what the stuff in the mistakes just hasn't been found yet (if there are mistakes, if not than it's just "None", but that would have to be 100% known thing that there are no mistakes to be said of).