That Moment Changed Everything: What's the Catch With S3's "11 Nines" Durability Claim?

https://s3.amazonaws.com/column/how-high-traffic-online-platforms-use-amazon-s3-for-secure-scalable-data-storage/index.html

Which questions about S3 durability will I answer and why do they matter? When Amazon S3 advertises "11 nines" durability - 99.999999999% - it sounds like an absolute safety net