I normally get a 50-70 WPM score on typing tests, but got a 6 on this. There was a fair amount of errors but surely 6 isn't the best representation of WPM with adjustment for errors.
I also am getting what I believe to be an inaccurate wpm. I am getting 30 but I normally score around 65wpm. It might be because it makes the mistake of counting actual words instead of 5 character chunks.
When you get to the end, it explains that it uses net WPM (NOT Gross WPM), which is error-adjusted to create an "effective" WPM.