It's fairly irrelevant for me, I always pay at least $450 and try to pay closer to $500 but it's good to know what "catch-up" I have to make in order to make it add to that amount. I honestly wish they'd take the postage, printing and labor costs that it takes to send all these notifications and just subtract them from the cost of my loan. It's NUTS that they don't allow you to receive e-notifications if you're enrolled in automatic debit.
On another note, sold back some books at Strand today and made $35. W00t!