DATAFILE PAGE SHOWS WRONG VALUE ON USED (MB) COLUMN

n :  11.2.0.3 version, Storage Management

select tablespace_name,bytes,(bytes/1024) Kilot,((bytes/1024)/1024) Mega
t,file_id from dba_free_space
where tablespace_name = 'VELVATS160M'
ORDER BY tablespace_name, file_id


TABLESPACE_NAME                     BYTES      KILOT      MEGAT    FILE_ID
------------------------------ ---------- ---------- ---------- ----------
VELVATS160M                     167772160     163840        160        600
VELVATS160M                     503316480     491520        480        603
VELVATS160M                    2013265920    1966080       1920       1107


form em

tablespaces

1-Used space is wrong, when you navigate to Datafile from Tablepace:

object name velva
                       alloctaed size (MB)      space used (MB)    
velvats160m     9.605                           7045


total allocated size GB 11.35
total used GB           8.15
total allocated free space GB 3.2


2-View Tablespace Name and you get wrong Used (MB) for datafile
                           size(MB)            USED (MB)