How does Amazon claime 11 9's of durability when the chance of an asteroid extinction event is roughly 1000x as high? This isn't a joke: I can't find any docum

How does Amazon claime 11 9's of durability when the chance of an asteroid extinction event is roughly 1000x as high? This isn't a joke: I can't find any documentation on the risk model that lets them estimate 11 9's and what class of risks it includes.