You will need to remove any vBulletin template code from postbit(_legacy)
that you intend to use with Postbit Tabs, otherwise it will display multiple
times.
EDIT:
You need to open blog_postbit_entries_link template and delete <dt>{vb:rawphrase blog_entries}</dt><dd><a href="{vb:link blog, {vb:raw post}, null, 'userid', 'blog_title'}">{vb:raw post.entries}</a></dd>
I forgot the Blogs come from vBulletin's own plugin, and not from postbit_legacy