This looks to be an issue with official Facebook button itself. Proper width is being set by WP Socializer but Facebook code is not honoring it. We have to wait for Facebook to fix it. You can see the bug in Facebook site itself. https://developers.facebook.com/docs/plugins/like-button/. Try changing the width with layout set as box_count.
For now temporarily, you may use the “Social icons” button with social counter turned on.