Why do the Packing List and Commercial Invoice have a different number of item lines?

In Patisco, the Packing List and Commercial Invoice are two tabs of the same Shipping Management document, using the same shipped items: quantities and carton counts follow the Packing List, and the Commercial Invoice only adds unit price and amount. They look different for these reasons: - The Commercial Invoice has "Additional Charges" (shipping, fees, etc.) at the bottom, which only appears on the Commercial Invoice, not on the Packing List. - On the Packing List, one item may appear as both a main carton and a tail carton. The tail carton is the remainder when a full carton can't be filled; it's a separate line in the data but counted with the main carton. Don't double-count when verifying quantities. - [Adjusted Commercial Invoice] is a separate copy where unit price and amount can differ from the Commercial Invoice, but quantities still match the Packing List. To change quantities or carton counts, go back to the [Packing List] tab to edit. The Commercial Invoice cannot change quantities separately.