[Plugin: YOURLS: WordPress to Twitter] Yourls plugin automatically creating shortlinks for old posts

I logged into my Yourls installation today and found hundreds of shortlinks created for posts written in years and months past. I can only assume these shortlinks were created by the Yourls plugin. I had to delete all these links because I didn’t want them. Is it possible to stop the plugin from automatically going into a link frenzy and creating unnecessary shortlinks for old posts? I only want the plugin to generate a shortlink and push it to Twitter when I write a *new* post.

http://wordpress.org/extend/plugins/yourls-wordpress-to-twitter/