When you listed that item, you chose Customer Delivery and decided that 87p is what you wanted to charge. The delivery method stated is Royal Mail 2nd Class letter.
That is the amount the buyer paid to you (eBay don’t even charge a BPF on it!!)
what you are seeing now is eBay’s pack link integration and it is recommending you Yodel.
you don’t have to use it. You could source your own postage outside of eBay