You can't. But then again, does it matter? Is it accurate? How do you know?
How popular a website is at best is a good guess. Even you don't really know because website statistics are subjective and difficult to measure precisely. What exactly is a visit? If a user surfs your site, stops for ten minutes, and then surfs it again, is that one visit or two? Were they reading a page for ten minutes? Or did they walk away? Is it the same person again or another user at the same computer?
As for how others determine what is popular it gets more difficult. They don't have access to your stats so they really have to get creative in determining popularity. Some use the data that passes through ISPs to determine site popularity. Others use sources like Alexa who use spyware to track users' surfing habits. These methods works pretty well for heavily trafficked websites but starts to suffer from inaccuracies as you move further down the scale.
So, back to one of my original questions, how do you know it is not accurate? You, too, don't have access to other sites' statistics and I am pretty sure you lack the means to mine the traffic of ISPs or create a massive spyware network to track hundreds of thousands or millions of users. So how do you know that popularity number isn't accurate? I bet the number being reported by that addon is more accurate then how popular you think your site is.
But, once again, who really cares? By looking at what "features" that addon supposedly offers I'd say no one who knows anything about websites is going to use it. That information it offers is useless to the average user and pretty much everyone else, too. The few people who will use either are clueless enough that they shouldn't be a concern to you or already know how useless the popularity metric really is therefore rendering it meaningless.