Factors than can impact speed test results

Speed test results could be less than the subscribed speed as its CPU generated traffic. This will be lesser than speed test done from a client device which is connected to Nokia Wifi Devices.
If you have another application consuming bandwidth (like a file downloading), it will affect the test results
Speed test traffic is not given any specific priority over other user traffic, so the variations could be present
At peak times, there is very often a drop in quality of connection with most ISPs. This is because many people are connected to the Internet through the ISP at that time. This will affect speed test results as well.