I created job as follows:

VARIABLE JOBNO NUMBER;
BEGIN
DBMS_JOB.SUBMIT(:JOBNO,'BEGIN UPDATE JOB_TEST SET RUNCOUNT = RUNCOUNT+1; COMMIT; END;',
SYSDATE,'SYSDATE + 2/1440');
END;
/

commit;

/I assume you ran commit after you created job/

this job increments runcount in job_test table. it executed immediately after I created it and ran every 2 min until I removed it.

by the way, job_queue_interval = 10 is a 10 sec interval for SNPn background process to wake up and check for jobs to run.
So, your init.ora parms look OK.