You can run the following sql to compute statistics :
You can view the statistics as in the picture:
try this sql to shrink:
however, this may give the following error due to the reasons here: http://agstamy.blogspot.it/2009/02/ora-10631-when-trying-to-shrink-table.html
SQL Error: ORA-10631: SHRINK clause should not be specified for this object
"SHRINK clause should not be specified for this object"
*Cause: It is incorrect to issue shrink on the object
*Action: Verify the object name and type and reissue the command
in this case, you may try by removing the indexes, shrinking the table and recreating the indexes.
btw, truncating the table gives you the space back!