LOBSEG SPACE ALLOCATION VALUE IN V$SEGMENT_STATISTICS <> BYTES IN DBA_SEGMENTS ??!

I need your help  to understand why i don't  have the same table  SIZE_MB between two query on my dabase  :?!!

1)

select  S.OBJECT_NAME, S.VALUE SIZE_MB

from V$SEGMENT_STATISTICS S

where   statistic_name in ('space used')

   AND object_name='PERSON'

    and owner='user1'

2)

SELECT   segment_name, ROUND(bytes/(1024*1024),2) SIZE_MB, 

FROM DBA_SEGMENTS

WHERE SEGMENT_TYPE IN ('TABLE', 'TABLE PARTITION', 'TABLE SUBPARTITION', 'INDEX', 'INDEX PARTITION', 'INDEX SUBPARTITION', 'TEMPORARY')

      AND SEGMENT_NAME='PERSON'

      AND segment_type = 'TABLE'

      AND OWNER = 'user1'

I  have a reference to this  Bug 4220436 : LOBSEG SPACE ALLOCATION VALUE IN V$SEGMENT_STATISTICS <> BYTES IN DBA_SEGMENTS,  But i can't found any documentation on Metalink