Robocars - Autonomous Drive, Self-driving, Driver-less cars

You might have mentioned that the Tesla driver was actually killed:

http://www.standard.co.uk/news/world/us-government-investigating-first-known-fatality-involving-selfdriving-car-after-tesla-ploughs-into-a3285576.html

The Tesla statement added: “This is the first known fatality in just over 130 million miles where Autopilot was activated.

“Among all vehicles in the US, there is a fatality every 94 million miles.”

And yes, it's not the same as 'self-driving'.

How do they know the 130 million miles figure? Computer tracking of these cars?