Hi Drashna,
I have remeasured the pool which does not resolve the issue.
I've formated a few of the drives, waiting for the data in the pool to re-duplicate in between formats, and have reduced the amount of 'other' data down to 165GB.
As you can understand I do not want to have to continue formatting disks to remove the 'other' data.
I am also concerned that this data may in fact be data that is not yet duplicated.
Regards