The SupplyRequest resource allows requesting only a single item. If a workflow requires requesting multiple items simultaneously, this is done using multiple instances of this resource. These instances can be linked in different ways, depending on the needs of the workflow.
Note that the Supply Request records the fact that a request was made. To actually act on that request, additional workflow beyond simply the existence of a Supply Request is required. This can be achieved by using an Task resource, with the Supply Request referenced from the Task.focus, or by using the SupplyRequest resource in the context of an messaging or service workflow where the request is explicit or implicit. The Supply Delivery resource represents the fulfillment as a result of Supply Request being acted upon.