If you switched from http to https, then the number of facebook shares & likes may not display correctly anymore. That’s because when a user likes/shares a page, the specific URL gets liked/shared, so if the URL changes (e.g. due to a switch to https) then the counts show 0 again.
The premium plugin fixes this by giving you the option to show an aggregate count of the likes/shares of both the http- and https-version of the page. So people can see again your hard-earned likes & shares! 🙂