If production has commenced and it is too late to cancel the units, You need to Force Close the Sales Order. That will tell Zedonk that you are not delivering these products to this client.
The order in the list is now showing a Red tick to indicate it is a 'Closed Order'
Sales Order is OPEN - Production Order raised - Projected Stock is ZERO
Sales Order is FORCE CLOSED - Stock Sold is reduced - PROJECTED STOCK is increased to reflect forecast surplus stock
Production is BOOKED IN - products received in Inventory CLOSING STOCK and surplus is now shown in AVAILABLE TO SELL.
For more information on Available to Sell figures