Even though they make a point of saying that this plugin does not count site visits from your computer, it does. And it does so every time you preview a post, or reload a page, or even when you update it. It even admits it does so by listing "WordPress Dashboard" as the source of the visit.
If you have thousands of visitors a day, this doesn't matter at all, and the plugin seems to do fine. But when you're starting up, and you're trying to measure which of your new posts are getting the most visits out of only several dozen, it's worthless because you can't subtract out your own clicks.
And yes, I used my correct API key from wordpress.com.