Grades 6–8 · Systems
How does delivery timing affect available stock?
A shop can receive enough items during a day and still run out while customers are waiting. Stock is the physical supply on hand at a particular moment. A delivery increases it, while supplying a request decreases it. If a request is lost when the shelf is empty, a delivery arriving afterward cannot supply that earlier customer.
In the diagramAn inventory ledger with event orderStart: 6Delivery: 4Start6 itemsReceive+4Request8 askedClose2 remainSupplied 8 · unmet 0 · end stock 2Unmet requests are lost; no automatic backorders
This explanation follows one delivery and one request in a stated order. If delivery comes first, its items join starting stock before demand is handled. If the request comes first, only starting stock is available then. The later delivery changes closing stock but does not automatically fill the earlier unmet request.
The illustrated starting stock is 6 items. A delivery of 4 arrives before a request for 8, making 10 available. Supplying all 8 leaves 2 items. If the same delivery came after that request, only 6 could be supplied then; 2 requests would remain unmet and the delivery would leave 4 items in stock.
In either order, closing stock equals starting stock plus received items minus supplied items. Unmet requests never make the physical stock negative. The same delivery and the same amount wanted can therefore produce different service outcomes: arriving early enough matters as well as arriving with enough items. A full shelf at closing does not prove that the shop met every request during the day.
About this explanation
The example follows one delivery and one request. Unmet requests are lost, not automatically backordered. It omits uncertain demand, costs, spoilage and rules for choosing an optimal order quantity.
Starting knowledge: Track a running balance and distinguish delivery from customer demand.
Sources
- OpenStax — Pulling It Together: Resource Planning
- OpenStax — Inventory Management