As you know when an item is bought eBay automatically add their charges such as commission to the seller's (my account) account. If I cancell a sale they expect an answer why I cancelled, otherwise I get will judged wrong with negative notification reflected on my file.
If you seriously plan to pay on 13 I will not take any more action (at the moment it is a notifivation) . When you pay everything will be sorted out by the eBay system.