The duplicate hunter shows you the performance of search terms over the past 30 days to highlight any duplicates. It does not mark off whether or not the search term has previously been added as a negative. If it was, it would naturally be removed from this list after not getting data after a period of time. New data is reported every 31 days.
If you have any other questions feel free to contact us at firstname.lastname@example.org. Happy Hunting! 🦡