It's not clear to me what the "per month" option means in Sub Notifications Options means. It would SEEM that it adds that amount per month subscribed. So if it was your intention to have month one be 1000, you would make the sign up 900 and the "per month" 100, so when they did it in the future, that would go to 200, 300,etc. and they would get 1100, 1200, etc.
Is my understanding of that correct?