AFAIC tblPO is for PO header data only - PO id, CreateDate, Dept, Creator, Supplier, etc.
PO line items belong in their own table and the received status could be there. However, line items may not all come in at once so you could have a status field with a value for every item record. You might also incorporate tblInvTransactions where you track inventory transactions and not try to calculate stock quantities from PO lines if that is the intent.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.