Axon Saga what is the purpose of SagaLifecycle.associateWith

Question

I'm trying to wrap my head around the Saga pattern of Axon framework.

Given this block of code:

public class OrderManagementSaga {

    private boolean paid = false;
    private boolean delivered = false;
    @Inject
    private transient CommandGateway commandGateway;

    @StartSaga
    @SagaEventHandler(associationProperty = "orderId")
    public void handle(OrderCreatedEvent event) {
        // client generated identifiers
        ShippingId shipmentId = createShipmentId();
        InvoiceId invoiceId = createInvoiceId();
        // associate the Saga with these values, before sending the commands
        associateWith("shipmentId", shipmentId);
        associateWith("invoiceId", invoiceId);
        // send the commands
        commandGateway.send(new PrepareShippingCommand(...));
        commandGateway.send(new CreateInvoiceCommand(...));
    }

    @SagaEventHandler(associationProperty = "shipmentId")
    public void handle(ShippingArrivedEvent event) {
        delivered = true;
        if (paid) { end(); }
    }

    @SagaEventHandler(associationProperty = "invoiceId")
    public void handle(InvoicePaidEvent event) {
        paid = true;
        if (delivered) { end(); }
    }

    // ...
}

The document say about @SagaEventHandler(associationProperty = "orderId"):

For example, consider an incoming Event with a method "String getOrderId()", which returns "123". If a method accepting this Event is annotated with @SagaEventHandler(associationProperty="orderId"), this Event is routed to all Sagas that have been associated with an AssociationValue with key "orderId" and value "123".

So there will be a lot of Saga instances, and associationProperty="orderId" will be used to match an Event to a Saga. So far so good.

But what is the purpose of SagaLifecycle.associateWith("paymentId", paymentId);? The document does not give an example like the case @SagaEventHandler(associationProperty = "orderId"). I still not understand it, please help