I will suggest testing the speed using the latest version of the speedtest-cli
Also, make sure to download the latest version of the binary and not a version that is available from your repositories as this might present wrong data.
Basically, the speedtest-cli command that comes out of the default apt repository is faulty and is not presenting correct details. What you should try doing is using the latest version of the speedtest-cli binary:
- wget https://raw.githubusercontent.com/sivel/speedtest-cli/master/speedtest.py
Then make run the test again:
Hope that this helps!