Combined postage when eBay controls postage. How is second item paid when not shown as despatched?

[somerset_vern]

eBay sends QR codes for items and charges the buyer separately for postage, but postage is included in the price paid.  The seller receives the winning bid price of the item.  My buyer won two items which I agreed to put into one parcel.  The buyer had already paid for both items, including postage on both.  Great eBaying as they say.
Have sent both items but the questions have arisen:
How does buyer reclaim the postage cost already paid for the second item (both items are lightweight totalling under 400 grams)?
How does seller get paid for second item when it cannot be shown as despatched or received?
There seem to be ways to send combined before buyer has paid, such as amended invoice, but not after payment has been made

[tobiasd4]

If SD label not used, buyer will get a refund.

This is why it's not possible for seller to combine postage. 

You will have to wait 14 days for payment of 2nd item.