That doesn't make it at all clear how pro-rata comes in to it, which is the issue here. Because you pay for the month up-front, the resting period basically means you forefeit the unused time in the month, you don't get the credits back? If you reconnect later in the month, you've already paid for it at the beginning of the month, so effectively lose the money in the rest period.
From the same link I posted:
“Resting period” means a period available to a Subscriber during which time he/she is not liable to pay for subscriptions;