The Order Lines list as a part of Purchase Order is intended to keep the list of ordered Inventory Parts and can contain the unlimited number of lines. Each Order Line has a Line Number and Release Number (the last one is auto incremented number for the lines where the same Inventory Part is specified).
Each Order Line can contain Part Number and Description (including Supplier specific Part Number and Description), Ordered Quantity, Purchase and Inventory Units of Measure, Unit Price in specified Currency, Line Total, Wanted and Confirmed Receipt Dates etc.
The actual Order Line Status, Arrived Quantity and Actual Arrival Date will be updated automatically during Order Life Cycle.