Yep, requires another request for a module. It should stop after you reach your maximum usage for that module. You receive a message that it has ended. On your Telcel page where you sign on, there is a counter that shows days as well as bytes used. Do it once and you'll get it. Confused the heck out of us and I think we lost a few pesos in the first round.
Once you get the hang of it, you'll love driving down the road, finding a signal and looking up info right there. Good luck. It'll all come together.