Speed test.Net Data usage :s

Picture links to a non-existing page. Error code 410.
Anyway, you sure you're not just doing that many Speed tests? If not, go into your settings and disable background data. That way it will only be used when you're actually testing it
If that doesn't work, delete the app and download the FCC's speed test app. Not as good in my opinion but it'll give you similar results :)