Use this notification to be reminded that there are openings which are still short on volunteers. The Maximum % full setting indicates how empty the slot must be.
One notification is generated for each slot meeting your criteria here, each with information about the relevant job slot.
In this example, with this event, a notification will only be generated if the slot has less than 75% of its required volunteers, is starting within 3 days from now and is in the job Hospitality.