Hi,
try to open you index.php file (you can find it here \wp-content\themes\shard\index.php)
and go to line 21 where you have this code:
$ABdev_title_bar_title = __('Posts Taged','ABdev_shard').' '.get_query_var('tag');
Just replace ‘Posts Taged’ with text that you like.
Cheers