How does the “Remove retention files for overlap policy” under Advanced Retention Policy work?

In general, daily snapshots followed by a weekly snapshot or a monthly snapshot, etc. will be removed; weekly snapshots followed by a monthly snapshot or a quarterly snapshot, etc. will be removed; and so on.

This is illustrated by the following example.
Assume today is 17 Jan 09, and the Advanced Retention Policy is as follows:

- Daily: retain for 7 days
- Weekly: retain for 4 weeks (the job will be performed on Saturday) 
- Monthly: retain for 3 months (the job will be performed on 1st of each month)

If “Remove retention files for overlap policy” is NOT enabled:
Then a total of 14 snapshots (7+4+3) will be kept on the server accordingly, i.e.:
(Daily): 10Jan09, 11Jan06, 12Jan09, 13Jan09, 14Jan09, 15Jan09, 16Jan09
(Weekly): 24Dec08, 31Dec08, 7Jan09, 14Jan09
(Monthly): 1Nov08, 1Dec08, 1Jan09

If “Remove retention files for overlap policy” is enabled:
Then only the following snapshots are kept: 1Nov08, 1Dec08, 1Jan09, 14Jan09, 15Jan09, 16Jan09.

Specifically, the weekly policy overrides the daily policy so 10Jan09, 11Jan09, 12Jan09 and 13Jan09 will be removed. The monthly policy overrides the weekly policy, and 24Dec08, 31Dec08 and 7Jan09 will be removed as well.