From https://www.apple.com/child-safety/ https://www.apple.com/child-safety/ “The threshold is set to provide an extremely high level of accuracy and ensures l

From https://www.apple.com/child-safety/ https://www.apple.com/child-safety/ “The threshold is set to provide an extremely high level of accuracy and ensures less than a one in one trillion chance per year of incorrectly flagging a given account.” How did they calculate this? Also, I can imagine more than a trillion photos being uploaded to iCloud a year.