Hi,

thinking a bit it's easy to undestand that the problem is not this metric nor the stats tracking of the component.
If all visitors is tracked with the same IP addres obviosluy it will be supposed to be a unique visitor.
The real problem is that different visitors can't access the website having the same IP address, so the problem should be researched rather outside the component and Joomla, i guess that there is a server firewall or similar that mask the IP address of visitors. Obviously i can't do nothing.