Table Fragmentation size issue

I am trying to find out table fragmentation and used below two queries( stats on this table collected very latest). I suppose dba_segment output size should be more than from dba_tables size output. But I am getting contradictory results. Please help someone explain what is wrong. Thanks in advance.

select sum(bytes)/1024/1024/1024 from dba_segments where segment_name='ZOSEC';

240.375GB

select table_name,avg_row_len,round(((blocks*16/1024)),2)||'MB' "TOTAL_SIZE",round((num_rows*avg_row_len/1024/1024),2)||'Mb' "ACTUAL_SIZE",round(((blocks*16/1024)-(num_rows*avg_row_len/1024/1024)),2) ||'MB' "FRAGMENTED_SPACE",(round(((blocks*16/1024)-(num_rows*avg_row_len/1024/1024)),2)/round(((blocks*16/1024)),2))*100 "percentage"from all_tables WHERE table_name='ZOSEC';