I'm using the "specific days" selector. I first select a few days and the time span. But when I fill in my availability I notice I made an error and go back to adjust the time window. However there's no way to modify the event's window once you create it, AFAICT, you can only delete this one and re-select the time window in a new one. This is pretty unintuitive as I would regard the time window as configurable.