The actual speeds for the service may be slower and vary due to many factors including type/source of content being downloaded, hardware and software configuration, the number of users and performance of interconnecting infrastructure not operated by TPG.
Devices connected by Wi-Fi may experience slower speeds than those connected by Ethernet cable.
We'd recommend having a read of this community article, which may help you check if the speed you're getting at the moment is within acceptable range.
This also includes troubleshooting on how the speed can be improved.
If you are connecting all your devices via Wi-Fi, this article may help as well : Easy Steps to Improve Wi-Fi Connection In Your Home
We have also received your query on Facebook. We can see that you have confirmed that the speed on your PCs are amazing and you're only experiencing the problem on your XBOX.
Feel free to search community for help or contact us if you need further assistance and we'd be glad to assist you.