Just place one line of code above the Visitor Stats 2 include line.
The second line Marks the visitor as 'Customer':
You can use any name you like, 'customer', 'contacted me', 'this person viewed my gallery' etc.
It's up to you, and you can change it anytime.
NOTE: Once a visitor is marked, they won't be re-marked by an automatic mark... only by a manual one. This is so you can recognise a visitor, rather than them changing names every time they buy from you, contact you or view your gallery etc.