Volume space utilization mismatch


Filesystem               total       used      avail capacity  Mounted on
/vol/abc/     2050GB     1131GB      919GB      55%  /vol/abc/
/vol/abc/.snapshot      512GB        0TB      512GB       0%  /vol/abc/.snapshot


 lun show -v /vol/abc/lun1
        /vol/abc/lun1    2.0t (2199291691008) (r/w, online, mapped)
                Serial#: AvKdX?CkBR7G
                Share: none
                Space Reservation: enabled
                Multiprotocol Type: vmware
                Maps: PBR04=96 PBR03=96 CLUSTER=96
                Occupied Size:    1.6t (1789095673856)
                Creation Time: Sun Apr 20 09:47:34 BST 2014
                Cluster Shared Volume Information: 0x0

Here, the used capacity is 1131GB and a 2TB LUN is provisioned from the volume which has space reservation enabled. How is this possible? Isnt the used capacity should be atleast 2TB in this case? Please explain.