It took me one or two times of doing it that I realized why some postings were showing up two times.
After you write your posting and you get the message to sit tight... etc.... you need to do just that... sit tight. If you click on the link to take you back here, for some reason the software then prints your posting two times.
You can correct it by clicking on the little paper and pencil icon. Once it takes you to the new screen, then click on the box that says Delete Post? After clicking then click on the Edit Post button... that will take care of the problem.