Module posting full article – Instapaper

When I set this up for instapaper, it seems to just post my entire post to instapaper.
Not good if you’re trying to do SEO and avoid duplicate content.
Is there a way I can disable it posting the entire post?
I’ve played around with the spintax and even tried taking %excerpt% out entirely, etc, but it just posts the whole post.

Any ideas?
Thanks.