We tried to order a product marked In Stock but the Proforma Invoice shows a long Estimated Delivery Time. Why?

If you place an order for a quantity more than 1, check the product availability in the Cart. For example, we have 5 pcs in stock and you order 6. The availability in the Cart switches from In Stock to Order when you change the Cart quantity to 6. The Proforma Invoice will show a long EDT (Estimated Delivery Time) for 6 pcs but a short EDT for 5 pcs.