We measure a total number of sessions within the payment date range.
As you can see in our pricing plans sessions are the cost driver.
A session is the period time a user is actively engaged with your website. With other words its your amount of visitors. I have to emphasize that it is not unique visitors but every session.
When you have implemented the tracking code on your website we start measuring the number of sessions you use.
If you don't have any Sleeknotes active we still count the number of sessions. This is why we highly recommend you to have a Sleeknote active at all time.