Upload speed

The upload speed is supposed to be 10 Mbps. If tests were performed with Wifi connection I would suggest to redo your tests with wired connection.
You should also try with different browsers. Someone has reported that upload speed is sometimes different when using different browser.

There are various factors that influence the speed you get on your mobile. Here are few of them:
The internet speed provided by your ISP.
Your router's ability to serve you the speeds.
Carrier network speed and signal strength.
ISP's service ability and network strength in your demographic area.
Congestion in your area.
Finally coming to your device, No of apps you are running in background.
The strength your device is receiving.
It really all depends, but the point of your study (regarding your data speed) should focus on consistency. It always 10mbps everyday ? More importantly what times of the day are you including in your testing ?
These are important factors to consider. Perhaps chart all this data on excel and see what you get. Then, probably approach fizz support, if you find that indeed that there is an issue.
Bst of luck!