A common five-field cron expression describes minute, hour, day of month, month, and day of week. For example, 30 9 * * 1-5 usually means 09:30 on weekdays. The exact scheduler matters: some add a seconds field, and interpretations of restricted day-of-month plus day-of-week can differ.
Use the cron parser to check the expression, then inspect its next several run times in the scheduler's configured timezone. Test across daylight-saving changes if the job is local-time sensitive. Also decide what happens when a run is missed or overlaps the next one. A correct string is only one part of a reliable scheduled task.
Akousa