Your clothing items are being sold with Ebay's Simple Delivery.
The buyer pays Ebay directly for postage, this amount does not go through your account and does not include an amount for packaging.
Ebay then produce a label or you can download and use a QR code.
Unless you list items with free postage/seller pays, you shouldn't be paying for postage.
Edit
Looking at your current listings, you have 19 items listed with free postage.
If you want the buyer to pay for postage and use Ebay Simple Delivery, you will need to change the postage on those items to 'buyer pays',
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)