A letter of credit triggers payment to the exporter only after the required pre-determined documents have been sent to a bank or financial institution.
If the quantity of products shipped out (as seen on the packing list and on the bill of lading) is outside the tolerance set in the letter of credit, it causes a discrepancy. In this case, the importer has the choice to accept it (in which case he can receive the shipment, and the supplier gets paid) or to refuse it.
Therefore, the buyer does not need to wire an advance payment that binds him to a potentially unethical foreign supplier. The importer keeps the freedom to refuse the products and cancel the payment if at least one document has a discrepancy, including if the products were of sub-standard quality.
Your information will be kept confidential.