How does Deletion Policy work ?

I was doing a test using a CIFS share on an Atmos VE at version 2.0.

There was a policy set for the sub-tenant which set retention at 2 minutes and deletion at 3 minutes.

A file was coped to the Atmos CIFS share and as expected it could not be deleted until the 2 minute retention had expired.
Another file was then copied to the CIFS share and left there with the expectation that it would be automatically deleted after 3 minutes.

After checking the file 5 min later it had not been deleted. After checking the next day it had not been deleted.

I assume this is because there is some periodic task which when run will delete and files that have exceeded their deletion date ?
Is this a correct ?
If it is correct how often are files which have passed their delete date deleted ?

Thanks.