Oracle job restarts everytime it is broken and unbroken

BEGIN
  SYS.DBMS_JOB.REMOVE(7777);
COMMIT;
END;
/
The propose of the job is to run only on Fridays at 9 . All jobs have to be broken at one time or the other for routine maintainance .
Surprisingly once the jobs are re enabled job 777 which brings the system to its knees kicks off .Your help will be greatly appreciated in this

--
-- JOB7777  (Job)
--
DECLARE
  X NUMBER;
BEGIN
  SYS.DBMS_JOB.SUBMIT
  ( job       => X


   ,what      => 'PurchaseAPI.TruckAvailability;'

   ,next_date => to_date('01/01/4000 00:00:00','dd/mm/yyyy

hh24:mi:ss')


   ,interval  => 'trunc(next_day(sysdate, ''FRI'')) + 21/24'

   ,no_parse  => FALSE

  );
  SYS.DBMS_OUTPUT.PUT_LINE('Job Number is: ' || to_char(x));
  SYS.DBMS_JOB.BROKEN
   (job    => X,
    broken => TRUE);
COMMIT;
END;
/

Massa