Move an old Time Machine folder (NOT volume!) to a different disk
You're probably seeing the result of hard links in the file system, which can result in counting the same file(s) more than once.

This is common in UNIX-like backup solutions, including Time Machine. The actual data usage is only 90GB, so a hard-link-friendly tool like rsync should handle the move correctly.

Per Wikipedia's article on hard links:


  The term is used in file systems which allow multiple hard links to be
  created for the same file.