Are you comfortable modifying SQL tables? You can clear the Banner Statistics this way. Its fairly simple, you just have to pay attention to what you are doing so that you don't accidentally modify something you shouldn't. Always perform a backup of your database prior to attempting anything.
Log into your CPanel of your hosted domain (separate from AbanteCart)
Scroll until you find "Databases".
Find and open "phpMyAdmin"
On the left side, find your Database table and click the + symbol
Find and click on "ab_banner_stat"
Towards the top-right of the screen click on "Operations"
Before performing this next step, please verify you are working in the ab_banner_stat table ONLY
To do this look at the very top of the page and you will see breadcrumbs. Make sure the last part of the breadcrumbs read Table: ab_banner_stat
Once verified, look towards the bottom and find and click "Empty the table (TRUNCATE)"
You can verify that you are about to truncate the ab_banner_stat table before clicking ok.
Once you are confident that you are on this table click "Ok".
Once complete, go back to your admin page and check the report (should be cleared)