As long as there is no case opened, copy these guidelines below, for your seller , instructions how to offer a partial refund.
Be aware, partial refunds cannot be enforced, do not let your seller make excuses, to allow you go over the 30 day timeline to claim for a full refund.
To offer a partial refund:
You may need a PC/laptop and not the app or mobile browser to do this, Chrome and Firefox work best with eBay.
If you are on My eBay Selling, go right of the item sold and from More Actions select Refund this item. Be careful to then add the correct amount of refund you wish to make, or you will refund the whole amount.
If you are on the Seller Hub, click on the item in Orders >> Posted and Awaiting your Feedback. Then top left click on View Order details. Far right from More Actions Drop down menu, you will see Refund this item.