Latest date of shipment is the latest date for loading on board/dispatch/taking in charge. There are two important point needs to be taken care of :
Latest date of shipment is the date of the transport document not your loading date from your factory. For example if credit requires for a bill of lading latest date of shipment is the date of bill of lading. No shipping company prints bill of lading until vessel daparture from the port of loading.
Latest date of shipment will apply only if the credit request a transport document. Otherwise we will get a late shipment discrepancy.