Weird, both have the same URL. How did that happen?
It's a duplicate because this submission has a space at the end of the url. It also has rel="nofollow" in the link. My guess is that the author submitted
The nofollow attribute is added automatically to articles newer than a few hours old to limit how effective SEO spam is.
Must have been the space.
The article IDs are different. One ends in 24 and the this one ends in 44.
He means the URLs that the articles are pointing to (http://www.9to5mac.com/macbook-brick). This site usually won't let you submit a dupe with the same URL.