An outbound delivery identifies the goods prepared for shipment against a sales order. VL01N creates the delivery reference; picking records the quantity prepared by the warehouse, and goods issue records the physical departure. A saved delivery with no goods issue has not yet reduced stock in this training client.
Partial deliveries leave part of the sales order unfulfilled. The delivered quantity must not exceed the remaining order quantity, and stock must support the goods issue. Read the task's shipping evidence before entering a quantity. Goods issue uses the material's valuation price for inventory and cost of goods sold, rather than the customer's selling price. That distinction will matter when you reconcile the financial entries later.