A filtering service is scheduled for its first download when you check Enable and click Apply. If you want to view or modify the schedule, or any of the attributes of the filtering service, use the browser-based management tool. Click Cache > click Filtering > select the intended list > click Modify.
You can change any of the original values you set when you created the service list item, and you can specify the frequency of downloads. You can also view or change when the next download will occur.
It is a good idea to schedule filter downloads for off-peak times on your network.