Freight charge deducted from invoice.

[chezzie26.123]

I have a listing of mutiple items.  I just sold 2 to one ebayer.  Ebay sent out the invoice showing a discount on postage.  See attached.  Therefore I virtually sent one item at no postage charge.  One item is $7.20 postage and 2 would have been $12.85. So who would have authorised the discount on the invoice.  Not me.  EBay already take their cut on the postage and now they have made it so I lose even more.  I do not inflate freight, it is a direct charge.  Can anyone advise me how this happens and how to stop it.