CookieHub Premium is charged by the number of page views for the previous month. Any domain created will start with a free 30 day trial and once completed, the total number of page views during that period will be used to calculate the amount due to keep using the service for the next month.
Page views is calculated based on the number of times the CookieHub widget is loaded from your site. It's may not be accurate number of page views as reported by Analytics services as the widget may be cached in the client's browser.
You can always see total page views for the current usage period in your CookieHub dashboard.