The alert form has a Campaign Objectives field with options to select: Sales, Leads, Engagement, Traffic, Awareness and App Promotion. If you leave everything unselected, the alert considers all campaigns. If you select one or more objectives, the metric is calculated only on campaigns with those objectives, using values derived from the real totals of those campaigns. This solves the problem of mixing contexts: an acceptable CPA for a messaging campaign isn't the same as for a sales campaign. If there's no active campaign today with the filtered objective, the alert simply doesn't fire (this avoids false alarms in Less than conditions). The notification tells you which objectives were in the filter.