||12-31-2013 07:00 AM
There could be 2 things that could explain this:
1 - When you format a partition a certain percentage (default is 5%, which is 200 Gb in your case) is allocated for root use only, this to make sure you are able to troubleshoot the partition if something goes wrong.
2 - There is a difference between 4 TB as mentioned by the manufacturer and 4 TB as mentioned by df. The first is based on 1000 being 1 Mb and the second on 1024 being 1 Mb.
Those 2 combined will account for the "missing" space.