When you handle customer orders and shipments with stored sales parts, they need to be reserved and picked on a specific inventory location. Whenever the parts are picked, the packing staff should enter what, how much, and from which inventory location they have picked the parts for each specific order and shipment.
The picking is reported in Warehouse Task page. You can confirm the picking by using Report Picking option or by using the Complete option in the My Warehouse Task page. You can pick both fewer and more parts than stated on the pick list. You only need to change the quantity on those order lines that deviate from the pick list; the remaining lines are reported according to the pick list. If you pick fewer parts than stated on the pick list line, the remaining quantity is released, unless you use shipment inventory and choose to keep remaining reservations at partial picking via the order type or shipment type. Partial picking is useful if you are not able to pick everything at the same time due to some constraint (e.g., what you pick does not fit on the forklift or in the handling unit you pack into), then you can pick multiple times until you have picked everything.
Picking can also be done on an aggregated level, either aggregated by handling unit or by location.
Note that for catch unit enabled parts, it is required to specify the catch quantity picked. This applies when you try to report picking, using less than the full quantity for the inventory part in stock.