This graph shows the monthly traffic on your site. Each bar represents one month, and the bar's height represents the total number of visitor sessions on your site during that month, regardless of whether they were first time visitors or return visitors (the exact number can be read at the bottom of each bar).
Important Note : by default, your account is set to count 'visitor sessions'. This ensures that a visitor loading your page several times in a row during the same browser session is only counted once (if that person comes back to your site 30 minutes or more after leaving it, a new visitor session will be counted). You can turn this option off by selecting 'Type of Tracking -> Test Mode' in the Control Panel ; this will force the counter to increase by one and the stats to add one visitor sesssion every time your pages is loaded. The test mode is useful when testing the counter after first installating it : reload your page a few times and you should see the counter increase by one each time (this would not happen in 'unique visitor' mode since we would only count the first loading of the counter and ignore subsequent loadings during the same browser session).