All of BurstNet's web hosting plans have Bandwidth Quotas, this is so we can offer a premium service and can make sure there is enough bandwidth for each of our customers and the service will never lag because we can foresee our Bandwidth Requirements.
The bandwidth usage is calculated on a calendar month, you will receive warnings above 80% usage.
If you have 1 day to go and you hit 80% usage then you probably don't need to do anything. If you hit 80% usage and there are 20 days left in the calendar month, then you might have to upgrade your plan or purchase some additional bandwidth.