Rules and Alerts for Traps with LA

I need to ultimately create an alert from a Trap rule configured in LA. However, I do not want the alert to Trigger until a certain number of the same traps has been received in a set period of time. I know that was an easy thing to do with the Legacy Trap Viewer, but can't seem to see how to do that in LA. Is it done in the Rule or in the Alert? Thanks.