There are more than 8499 pages on the site. There's at least one page for each apronym, one or more for each category, alphabetical, or apronymist listing, the different versions of those for the online stack, and whether you show only perfect apronyms. Also, the site is accessible from apronyms.com, acronyms.co.nz,
www.apronyms.com and
www.acronyms.co.nz, and I have noticed sometimes that Google has the same page shown more than once through the various domains.
It's not all just from the site itself though... many other sites link to this site. Especially since Apronyms was a Yahoo pick... a lot of other sites blindly copy links from the Yahoo picks. You can get an estimate of how many of the hits are external by clicking through to the last page of results... by default Google only shows the results which are sufficiently different from each other to be worth looking through. There are 131 for apronyms and 248 for apronym.
Something really spooky that I've noticed sometimes is that on different pages of results, Google will claim there's a different number of results in the blue bar along the top. I can't get that to happen now, perhaps they've fixed it, but it used to be quite common.