Choose 'Only when full' to clear the Results Window contents only when the list is full (the list can contain about 8000 items).
Choose 'Except in Scan/Repair & Eject' to clear the Results Window contents at the beginning of every new operation, except when 'Scan & Eject' or 'Repair & Eject' are selected.
Choose 'Every operation' to clear the Results Window at the beginning of each new operation.