What qualifies an arbitrary file/folder as being counted under user's data usage quota?

Question

A user asks,

"What qualifies an arbitrary file/folder as being counted under user's data usage quota? Is it based on location, ownership, etc?  If user A has a disk usage quota of 5 GB, is user A limited by the cumulative data size of all three users sharing data under that home folder? Is user A instead limited only by the directories/files owned by it?"

Answer 1

Only folders of which a given account is the owner is included in its quota. Any subfolders that are owned by other users are not included in the data usage quota of the owner of the parent folder.