No duplicates in "DUPLICATE" category

[frankdarwin]

I copied 105 photos in IMatch from one folder to another folder on another drive.
Now I expected to see these 105 photos in the "DUPLICATE" category. But this category is empty (see attachment "Category DUPLICATES.jpg").

But if I select one of these photos and run "Search Duplicates", I get hits and they are displayed in "Search Result" (see attachment "Search Result.jpg").

What is the reason for this?

[Mario]

This category is used when importing files, depending on your duplicate check settings (Edit > Preferences > Indexing). Press <F1> in that dialog to open the help.