Receiving duplicate alert emails


We are using Grafana v6.6.

I have been getting alert emails in pairs - one with the subject “[No Data] Developer Portal DEV Error Logs alert” and the other with the subject “[OK] Developer Portal DEV Error Logs alert”

I tried reading the v6.6 documentation on how the For and No Data settings are related but am confused by it. I guess these settings have something to do why I always get emails in pairs instead of a single email?

The intended behavior is to send me one alert email if one error is logged in Elasticsearch within a one-hour period.

Here is the current rule settings: