All speed test application/software measures the network throughput between any two given points on the internet (your machine and the test machine) at a given moment and all speed test sites are using different server location that caused different test result.
The only way to measure that accurately is to use our speed test client but you may also try to use www.speedtest.net.
We'd like to set your expectation that, actual throughput speeds may be slower and could vary due to many factors including type/source of content being downloaded, hardware and software configuration, the number of users simultaneously using the network and performance of interconnecting infrastructure not operated by TPG. Devices connected by Wi-Fi may experience slower speeds than those connected by Ethernet cable.
Let us know should you require further assistance.