A Telstra customer ripped through a mammoth 425GB of mobile data during the telco's free data offering on Sunday.

Telstra made the offer to its mobile customers as an apology for the "embarrassing human error" which caused widespread network outage last Tuesday.

425GB of data is more than enough to download all five seasons of Game of Thrones in high definition – four times over.

The data-hungry customer, John, from Rhodes in Sydney, said he downloaded all 25 seasons of the Discovery Channel's How It's Made; a "few other random TV show seasons"; and synced his entire Steam computer game library – 172 games in total – to a portable hard drive.