LOB SEGMENT SIZE issue - 10.2.0.4

Hi,

On one of our 10.2.0.4 database, we have a table with BLOB column and we are trying to determine its size and storage requirements

select sum(bytes) from user_segments where segment_name in
(select segment_name from user_lobs where table_name='TABLE_A' and column_name='BLOB_COLUMN')

          SUM(BYTES)                                                                                                   
--------------------                                                                                                   
         48,282,730,496                                                                                                   

select sum(dbms_lob.getlength(BLOB_COLUMN)) from TABLE_A

SUM(DBMS_LOB.GETLENGTH(BLOB_COLUMN))                                                                                       
-----------------------------------                                                                                     
                      6,596,801,277                                                                                       

Here is how the table was initially created .....
                                                                               
  CREATE TABLE TABLE_A                                         
  ........                                                 
   LOB ("BLOB_COLUMN") STORE AS (                                                    
  TABLESPACE "APPS_DATA" ENABLE STORAGE IN ROW CHUNK 8192 PCTVERSION 10    
  NOCACHE LOGGING  ......                                                            

Can someone please explain: