reorg- tablespace size increased

db2 9.5 .05
aix-6.1

After Performing RE-ORG on a table,
the tablespace size increased? How to get back that space

I performed re-org on a table (table size16gb ) in tablespace tbspid-8
Table space is Automated type , four containers defined on it.

--> db2 reorg table tab16

After reorg performed 4gb space on each container used.

befor reorg 20 gb of free space available on each container. after reorg 16gb free space isavailable on all containers.
I checked tablespace 8 which conatain the table tah i reorged
The High Water Mark pages is went high.
NOw
HOW CAN I RECLAIM THAT SPACE?