SQL & PL/SQL :: Understanding Dba_tab_modifications

This is the 10.2.0.4.0 database. To collect the object statistics, we are using the default GATHER_STATS_JOB. Totally I have 930 objects in my schema. but when I check the user_tab_modifications,it is only showing 344 objects. To understand the real concept, I have taken the below table for my analysis.

The below mentioned table got 3.7% changes since the last analyze.

1.) Why this table is not showing in dba_tab_modifications table?
2.) If 6.4% of changes happened in this table now, will oracle analyze this table today night?
3.) If your answer is 'YES' for the 2nd question, where it is keeping the information about 3.7% changes, since there is no information in dba_tab_modifications about this table?
4.) If your answer is 'NO' for the 2nd question,why it won't get analyzed?
5.) will oracle purge the older data from dba_tab_modifications table? if yes what is the frequency of this purging activity?

SQL> select count(*) from orca1;
COUNT(*)
----------
4493437

SQL> select TABLE_NAME,LAST_ANALYZED,NUM_ROWS,monitoring from user_tables where table_name='ORCA1';

TABLE_NAME LAST_ANAL NUM_ROWS MON
------------------------------ --------- ---------- ---
ORCA1 30-AUG-10 4332300 YES

SQL> select * from all_tab_modifications where table_name = 'ORCA1';

no rows selected.