Add this.com viral lift

I've started using addthis.com on VSC and I'mconfused by the concept of viral lift. And i quote:

Viral lift is the percentage increase in traffic due to shares and clicks. Essentially, viral lift shows you how viral your content is – if your shares are getting a lot of clicks, your viral lift percentage will be high.

The AddThis Analytic’s viral lift feature is a valuable tool in making editorial decisions and tailoring future content.  It allows you, as a publisher, to see what shares are sending the most traffic back to your site. If you head into your analytics dashboard, you will see that we flag a page as viral if it’s generating more clicks than shares. Then head into the Content tab, sort by clicks and you can easily see what content is really resonating.

End quote. I'm confused in that I feel that if content has a high share to visit ratio, it's already worth flagging it as having some viral potential. In fact, if people are sharing it, its a GREAT thing. A second question is whether the shares generate cliks. This could be driven by the quality of your page title, image , and meta description which is what shows up on a Facebook share.