I just don’t see in any way how the duplicate post addresses how the system number is generated.

How exactly can that other post explain what adds up to 60 GB?

@grgarside see above ^^^

@bmike You're right that it doesn't show precisely what comprises the System category, but DaisyDisk/etc will show the folders that comprise any usage on the system, including the system category, so it's a broader scope but that's how canonicals usually work. I've reopened it, I look forward to seeing your answer!