In practice, nearly every file in the WinSxS directory is a “hard link” to the physical files elsewhere on the system—meaning that the files are not actually in this directory. For instance in the WinSxS there might be a file called advapi32.dll that takes up >700K however what’s being reported is a hard link to the actual file that lives in the Windows\System32, and it will be counted twice (or more) when simply looking at the individual directories from Windows Explorer.