To delete files in Decloner Trash:

Select files to delete by clicking them, holding down the Command key (⌘) for multiple selection.

Click Delete button to move selected files to system Trash.
Click Delete & Link button to move selected files to system Trash and replace them with aliases (bookmarks) to the remaining file.
Click Put Back button to restore the selected files and remove them from Decloner Trash.

To make Decloner stop deleting files, click Stop button on the right of the progress indicator.
You cannot stop Decloner while it communicates with iPhoto or Aperture.