12c How to Limit incident metric email alerts per time period

 I have set up an out of memory rule to send an email and page when the Out Of Memory incident occurs in a database.

The problem is when this occurred this week in a dev instance here there were dozens of ORA-4031 alerts in a short span of time in the alert log and OEM seems to send an email  for each entry.

I would like it to be able to only send one email no matter how many times it occurred in the alert log in the time period that was scanned.

Does any one know if there is a way to accomplish that?  I can see a number of occurrences threshold on the metric. That doesn't seem like it fits the bill though as I would want it to email if 1 occurrence or if 20 occurrences in the 5 minute period. I just want it to email only once in both cases.