In Purchase Order Preparation, I receive a message ‘This purchase order is part of Contract (#). All updates to line and shipment quantity and date information must be made through the Contract screens’ what does this message mean?

This message appears because this PO is part of a contract (not a stand-alone PO) any changes to line, shipment quantity and date must be done through Contracts. Select Contracts, contract preparation, prepare, on the PO side edit as needed