Can’t Change Snippet for Twitter Post

While the plugin has been working great for pages, not so well for posts. When I duplicate a post whatever snippet or description information associated with the original post can’t be changed when posted to Twitter no matter how much I try to edit the duplicate post. I’m a new user so it’s entirely possible I’m missing some detail in my editing, but the inability to change the snippet or description means I can’t really use the plugin for posts. Thoughts on what I’m doing wrong?

The page I need help with: [log in to see the link]