oracle run duration to number

1SELECT JOB_NAME,
2       avg(extract(DAY FROM run_duration) * 24 * 60 * 60
3               + extract(HOUR FROM run_duration) * 60 * 60
4               + extract(MINUTE FROM run_duration) * 60
5               + extract(SECOND FROM run_duration))
6FROM DBA_SCHEDULER_JOB_RUN_DETAILS
7WHERE JOB_NAME = 'my_job_name'
8GROUP BY JOB_NAME;