Looks like you have this set to go out using the Calendar, something I've never used on Groups.io.? Can you provide a short overview for those of us who might like to send a regular monthly message like this to members?
I set up GMF's reminder before the Guidelines feature that Bruce mentioned existed. You might prefer to used that method. On the other hand, using a calendar Event gives you great flexibility in scheduling, at the cost of some boilerplate content and system hashtags. See also: /g/GroupManagersForum/message/3749