Difference between dba_segments and dba_extents

 Any idea about the reason for Difference between dba_segments and dba_extents , 11g DB
SQL> select sum(bytes)/1024/1024 as sum_used_via_segments
2 from dba_segments
3 where tablespace_name='ARISDATA'
4 and segment_name not like 'BIN$%';

SUM_USED_VIA_SEGMENTS
---------------------
5282,6875

SQL> select sum(bytes)/1024/1024 as sum_used_via_extents
2 from dba_extents
3 where tablespace_name='ARISDATA';

SUM_USED_VIA_EXTENTS
--------------------
5188,6875

SQL> select owner, segment_name, partition_name, segment_type, tablespace_name,header_block, blocks
2 from dba_segments
3 where tablespace_name='ARISDATA'
4 and segment_name not in(
5 select segment_name
6 from dba_extents
7 where tablespace_name='ARISDATA'