Are you sure you are not mixing up your bits with your bytes? Connection speed is measured in Mbps, download volume in MB. There are 8 bits per byte so a file download at 5-7 megabytes per second would roughly equate to a speed of 40-56 megabits per second.
Is the router still connected at the test socket?
I've checked the connection stats and your line is showing in sync at 51.5mb. If the router has been at the test socket for 48hrs then I can pass this over to our Network Team for investigation.
I'm getting a 38 download and a 16 upload. Which with the plan I'm on should be able to support streaming/downloading from multiple devices. But as soon 2 for example start watching or downloading, speeds drop and start video starts freezing or going in lower quality. Plus like I said my download has never been over 6mbps when downloading anything. Takes me a few hours to download a 20gb file for example.
Could I just confirm, are these devices connected wired or wireless when the throughput speed drops? As the throughput speed is also a bit lower than the sync speed, could you trying switching the router off for a full 30 minutes and then run the speed test again please.