To see a full breakdown of your invoice, on your My eBay page, at the top, select Summary>>Account tab, or, if you are on the Seller Hub page, select Shortcuts , then Site Preferences>> Seller Account >> Invoices and there, scroll down a little to the link All Selling Activity, that will give you a full breakdown of your invoice.
If there is something there which needs explaining, please contact eBay Customer Services, they have full access to your account, and can explain any fee for you.
Use a desktop browser, not a mobile browser, and not an app to manage this.
