Thru supports the mappings of retention rules at multiple levels.
Which then requires a definition of precedence.
A file is subject to the rule which is closest to it according to the following diagram.
As you can see, there is a way to define an exclusive user rule which shields the user from all other rules in the system, including rules which may be created in the future.
File type rules are enforced side-by-side with all other rules except exclusive user and file rules.
This was done so file type rules are still enforced even if other rules are defined.
Side-by-side means that the file will expire when the first of the file type or the other rule goes into effect.