On your admin panel, you can see detailed statistics about users and countries. These are live results and updated by visitors realy time. If they leave, they will be offline. If they stay, they will be stay. You will also see your old buyers, so you can contact with them right away...
Plugin will add itself automatically. The live counts will be updated live without refreshing the page! (This option can be disabled easily on the admin panel while keeping the stats.)
It is so easy to install, and configure with the admin panel. Just copy the file that you download to plugin folder and that's all, system will be installed.