In this dialog 1-Click Duplicate Delete for Outlook presents all the duplicates that it found. Simply place a check mark at the ones you want to remove. You can either click on the little boxes (for groups) or on the check mark/X.
Properties (e.g. the name) that are identical within the group are displayed faded. If they are not identical, they are shown in stronger colors.
Icons in the upper right corner:
Three pages: Close all folders in the list and show only the groups
Folder: Show groups and folders
One page: Show all (Groups, folders and files)
Symbols in the list:
Red question mark: This entry still waits for a confirmation from you and is not approved for deleting.
Green check mark: This version will be kept
Red X. This version will be deleted