If a supplier has supplied a product that is equivalent and functionally the same as the the one you ordered, or additional like items not on the original order, you can track this change correctly in WorkGuru when receiving the purchase order.

From the relevant approved purchase order's detail page, click Receive Purchase Order.

Receive the PO as normal with the information from the supplier invoice if you have it.  If not, leave the invoice fields blank to complete when received.  For the ordered product line item, ensure a Received Qty of 0 is selected.   As the recieved qty does not match the ordered for this line, WorkGuru will prompt for a backorder - click Cancel when prompted.  You can confirm the line is not backordered if the the Create a backorder checkbox is NOT selected.

Click the Add Product button and search for the substituted SKU or Name to add to the order.  Enter the Received Qty that was sent for the new product line.  Repeat steps 2 - 3 as required.  Click Save to receive the updated order into stock.

This process will update the PO correctly so you can track both what you originally ordered (received 0)and what was substituted (ordered 0).