Modification date for group - how is it arrived at

DEVONthink
1

Should it not be the most recent modification group for items in the group?

More description below:

I have a folder / group of sub-groups, files within sub-groups, like so

group a
-- sub-group a1
  -- a1f1
-- sub-group a2
  -- a2f1

If I edit a1f1, the modified date of a1 does not appear to change.
Would like to be able to sort a1, a2 sub-groups, based on whichever sub-group has the most recent modified file.

Could not find the answer in the discussions here, nor in the help.

Thank you.

2

The modification date of groups is independent, e.g. adding/removing items to/from a group updates it.

3

Ok got it. Thanks for the reply.