Oracle Database Discussions

I was checking space for specific tables and found intresting thing about blocks column in different tables/view.

In dba_tables. I checked that table is having 496 block according to dba_tables and 512 blocks according to dba_extents.

Here is code and output.

SELECT TABLE_NAME,
       TABLESPACE_NAME,
       NUM_ROWS,
       BLOCKS,
       AVG_ROW_LEN,
       SAMPLE_SIZE,
       LAST_ANALYZED
  FROM dba_tables
 WHERE 
 table_name='DLR_DETAILS_TEST';

output

DLR_DETAILS_TEST
DATA01
32853
496
31
32853
3/13/2014 10:01:33 PM

And Query#2

select bytes,segment_name,blocks from dba_extents
where segment_name='DLR_DETAILS_TEST' and owner='HR';

output has long list and in excel I found total it has 512 blocks.

Just a curious question WHY IS THAT?

OS : redhat 6 linux

DB : Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

Thanks.