For that page, the twitter:title and twitter:description tags are identical, so that’s why the text appears twice.
The validator shows this error for other URLs on your site:
ERROR: Required meta tag missing (twitter:text:description)
This indicates that there is no text in the twitter:description tag. With Wordpress, the most common reason that I’ve seen for this is when a plugin is trying to populate the description field from the article excerpt, but there is no excerpt set, so the field is blank.