It's hard for us to answer correctly as we have no access to your account, but this will show you a breakdown of your transactions, fees paid , postage, promotion - ad fees.
https://www.ebay.co.uk/sh/fin/transactions
If this still doesn't add up for you, then contact eBay Customer Services as they do have that access and can explain any fee for you.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@chloe_b5