Keep in mind these basic definitions when working with CAPITAL:
Qty = quantity the customer has ordered
Allocated = the quantity you have reserved or allocated for that customer.
(Hopefully this will be the quantity you will pick for the customer, assuming you have enough stock available.)
Picked = The quantity your warehouse staff have actually picked.
The allocated quantity tells the warehouse to go pick that quantity. If a warehouse operator decides to do a partial ship, presumably because the full quantity ordered is not available for picking and packing, then the "suggested pick quantity" (Allocated) needs to be set to zero, otherwise the warehouse operator will be asked to pick the remainder of the same order again.
For example, if the operator is asked to pick and pack 5 units, and only 4 are in good condition, and these are packed and shipped, the Allocation quantity must to reset to zero once he has finished with that transaction.
If the Allocated quantity is left with a 1 remainder, then the operator will be presented with the same order number to pick again, with a unit of 1 to pick. There is no point looking at the same transaction again, since the warehouse operator has already established that the item for that transaction is not available.