Issue with Facebook share button

Hello!
At first, i wanted to thank you for a great plugin. The issue is with FB share button is not centered properly (1px at the down). Here’s the screen – http://i.imgur.com/qZK5DgH.jpg

Sometimes i am being pedantic 😉 Is there any way to fix it?
Thanks and regards!

https://wordpress.org/plugins/really-simple-facebook-twitter-share-buttons/
The issue is only on Firefox.
(Udostępnij – share)