POP Forums measures usage by topic views, because that's where the real action is on your forum. Others count the views of profiles and topic lists and whatever. A topic view happens whenever a user (or robot) navigates to a topic. When they scroll and additional pages appear, that does not account as an additional view. You can monitor your topic view count at any time. The total updates overnight and is displayed in the management site. If you end a month above the quota for your current plan, you'll be automatically upgraded to the plan that will cover your usage.