Monitoring stops when the monthly maximum is reached. This means your monitoring might not show data at the end of the month, when the maximum was reached already.
Do not that although no more data is stored, their could still be traffic. This will go on a fair use policy basis.
If you want to stay within the maximum though, you could do one or a combination of the following:
Only track specific devices, such as mobile. This could be configured in our monitoring, or you could do this in your (Google or Adobe) Tag Manager;
Manage your URL's in our tooling, setting samplingrates per group of pages or temporarily inactivate high-traffic pages.