The shippingCount you can find when you query PO, is the initial purchase quantity where returned quantity is not reflected.
You can find returned quantity from cancelCount.
- shippingCount = Purchase quantity of an order
- holdCountForCancel = Canceled and to-be-refunded quantity
- cancelCount = Quantity for which cancellation is confirmed.
- Orderable count = shippingCount - (holdCountForCancel + cancelCount)