The Sale Unit field is a four character alphanumeric field used to describe the type of packaging in which a product is sold (e.g., each, case, can, 6pk, feet, gal, etc.).
It is available to be printed on sales invoices/receipts, price tags, shelf labels, and on some reports.
The Sale Unit is not updated and has no effect on Inventory quantities.
See:
Inventory Database - Main Screen Fields