By configuring an update window you are able to control when devices are allowed to download new content. By default a device will check every 30 minutes for any changes to it's schedule, content, etc. When the update window feature is enabled, devices will only be able to update during the time slots (windows) configured. This is useful for keeping your devices from updating during regular business hours.
In this example devices will only update between the hours of 10PM and 5AM.