Pallet Variation in Sales Order

Hello, I have the following scenario:

the client is a manufacturer. He is creating work orders in manufacturing and producing items. As an estimation during work orders, they add X quantites of wooden pallets to be considered (cost wise) during the total costing procedure.

The problem is that sometimes, during the shipment and the creation of the sales order, there is a physical variance of the quantity if wooden pallet. For example, instead of using X quantities, they are using X + 1, which creates a difference in on hand quantities of wooden pallet, and the cost will increase.

Desired result:

The client wants the flexibility of adjusting the wooden pallets quantities in the sales order with specific conditions: