Notification pops up again after dismissing it

I frequently (maybe always?) receive duplicate notifications for this event:

Just now at 11:00 EST, I received the expected notification for the event. I clicked dismiss, and about 1 minute later I received the same notification pop-up. As far as I can tell, I’ve correctly set it up to receive only one notification, and clicking dismiss should cause it to not notify me again. Is there something else I should be checking to stop this from double notifying me every week? Thanks!

In your screenshot, next to the “Save & Close” button, there’s a calendar selection field.
Check if more than one calendar is listed in that field when you expand it.
The appointment might be in two calendars. If so, you’ll naturally receive the reminder from each one.

Regards, DataShark

Thank you, I have only one calendar selected for the event.

Okay, then I’m afraid I have no further ideas.