It depends. If you are on our Free Plan the timer will no longer render. All of our premium plans allow for overage. This means that your timer will continue to show, and you will get billed on a per credit basis at the end of your billing cycle. The overage price per credit differs per plan and are listed on the pricing page: http://motionmailapp.com/pricing
For example: you are signed up for the Bootstrap plan, but you use up 120,000 credits instead of the allotted 100,000. At the end of the billing cycle, you will be charged an additional 20,000 * $0.0001 = $2 for overages.