Cron Examples:
Every week on Sunday at midnight: H H * * 0 (default)
Every day at midnight: H 0 * * *
Every 6 hours: H H/6 * * *
Every Monday at 9am: H 9 * * 1
Every 4 hours: 0 */4 * * *
Every hour: 0 * * * *

The discovery task checks every minute if the cron expression matches the current time and only executes when it matches.