If this check box is selected, all purchase order lines that are processed in the Process Delivered Purchase Orders (tdpur4223m000) session and that fall in the defined period, are taken into account when calculating the vendor rating. As a result, LN calculates totally new ratings that are fully based on the data in the purchase order lines' history.
If this check box is cleared, only the net changes are taken into account. So, only the purchase order lines that are newly processed in the Process Delivered Purchase Orders (tdpur4223m000) session and fall in the defined periods, are taken into account.