How to state the amount when issuing a Purchase Certificate for goods purchased from multiple manufacturers

I am planning to issue a Purchase Certificate after purchasing cosmetics from two domestic manufacturers (A and B) for export. For example, let's assume there are separate export offer prices for the goods purchased from Company A and Company B, and the export customs clearance is filed as an FOB declaration based on the total combined amount of both companies' goods. In this case, when issuing the Purchase Certificate for the goods purchased from Company A, I would like to inquire whether I should enter the entire total declared value (FOB) from field 46 of the export permit, or if I should enter the export offer prices for Company A and Company B separately.