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In the Quantity column, you can specify the item quantity and in the UOM column, you can select an UOM for the item if the Multiple UOMs per Item option is selected on the Administration > Settings > Purchasing and Warehouses form.

The Available column shows the quantity of the item currently available in the warehouse.

The Specification column is available if the Use Sets for Sales option is selected on the Administration > Settings > Purchasing and Warehouses form, and can select a specification to be used for the item if item is a Set.Click  Click the Set Components button on the toolbar to specify the components for the set.The Available field shows the quantity of the item currently available in the warehouse on the document date.

The tab toolbar buttons 

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