Deadline for issuing a Local L/C (Purchase Confirmation) when the purchase amount exceeds the sales amount

The transaction structure is A (domestic manufacturer), B (domestic exporter), C (overseas buyer), and D (our company). For example, on a specific date, A sold products to D and issued a tax invoice; subsequently, D sold portions of that quantity to B and C respectively and issued tax invoices. On the same day, A requested D to issue a Purchase Confirmation, but D currently still has unsold inventory remaining. While it would be ideal to purchase only the quantity intended for sale, various circumstances often lead to purchasing more than the planned sales quantity. In this case, I would like to inquire about the deadline for issuing the Purchase Confirmation for the products initially purchased.