There’s no support at the moment for single-line multiple shortcode.
You can try an ugly CSS workaround like this:
<style>#single-line .really_simple_share, #single-line .really_simple_share_clearfix { float: left; clear: none; }</style>
<div id="single-line">[really_simple_share button="twitter"][really_simple_share button="google1"]</div><div style="clear:both"></div>
A better solution is to add the following to your stylesheet:
.really_simple_share_facebook_like,
.really_simple_share_twitter,
.really_simple_share_linkedin,
.really_simple_share_pinterest,
.really_simple_share_google1,
.really_simple_share_digg,
.really_simple_share_stumbleupon,
.really_simple_share_reddit,
.really_simple_share_flattr,
.really_simple_share_tumblr,
.really_simple_share_facebook_share,
.really_simple_share {
float: left;
clear: none;
}
.really_simple_share_facebook_like:after,
.really_simple_share_twitter:after,
.really_simple_share_linkedin:after,
.really_simple_share_pinterest:after,
.really_simple_share_google1:after,
.really_simple_share_digg:after,
.really_simple_share_stumbleupon:after,
.really_simple_share_reddit:after,
.really_simple_share_flattr:after,
.really_simple_share_tumblr:after,
.really_simple_share_facebook_share:after,
.really_simple_share:after {
clear:both;
}