Gecko85
Explorer
These numbers are problematic.
If you looked, say, here, you get a very different range:
http://www.theresaragan.com/salesrankingchart.html
Amazon doesn't actually release this info, or I don't think they do, so that may be part of the problem.
Yeah, definitely "best guess". Interesting how the best guess for those two sites are so different. Reality is probably somewhere in the middle. Regardless, as has been pointed out, being in or around the top 100 for this long is a very good sign no matter what.