With no authority, a blog has a ranking of 7,966,799th most popular blog in the universe. To me this does not suggest there are 7,966,799 blogs being indexed, but rather that there are 7,966,799 -1 = 7,966,798 blogs with an authority of 1. I guess it could go either way, but that is how I am guessing they designed it. This only means there are more than 8 million blogs, I just don't know how many more.
Some sample numbers at the low end include:
These numbers are interesting and show how many blogs have the same authority. And yes, there are two different numbers for an authority of one. I'm just recording what I see. I'm not sure of the reason for this yet.