Final answer:
The packing slip may show a different number of items than what was actually shipped, due to packing or document updating errors.
Step-by-step explanation:
The document that may show a number of items which are different from the number of items actually shipped to a customer is the packing slip. The packing slip is supposed to reflect what is included in the shipment, but sometimes it may not match the actual items shipped due to errors in packing or updating the document. In contrast, a completed picking ticket is used in the warehouse to gather the items for shipment and should match the items picked, the bill of lading is a legal document between the shipper and carrier and should reflect what the carrier has accepted to transport, and the sales order reflects what the customer ordered, not necessarily what is shipped.