Once an item has been added to a shipment you can only change the quantity (qty) by the methods below:

To change the qty of the item you can double-click on the Qty field. ScanPower only allows you to reduce the quantity. Currently, you must go into the Seller Central Shipping Queue to increase the quantity of an item. You may also scan it into the same shipment through ScanPower List to attempt to add more quantity to the existing shipment.