Wrap your code (span tags) in a container and reset css box-sizing property to content-box
of this spans (see also: Right border of the AddThis counter missing with Twitter's Bootstrap 3):
your html:
<div id="sharethis">
<span class='st_sharethis_hcount' displayText='ShareThis'></span>
<span class='st_facebook_hcount' displayText='Facebook'></span>
<span class='st_twitter_hcount' displayText='Tweet'></span>
<span class='st_linkedin_hcount' displayText='LinkedIn'></span>
<span class='st_pinterest_hcount' displayText='Pinterest'></span>
<span class='st_email_hcount' displayText='Email'></span>
</div>
css (add after the Bootstrap CSS):
#sharethis span
{
-webkit-box-sizing: content-box;
-moz-box-sizing: content-box;
box-sizing: content-box;
}