Strange Numbers

Now I know that Amazon sales ranking figures are notoriously difficult to understand, but a sudden change last Wednesday has made me curious to know exactly what they might mean in my case. Thankfully, because I have opted to be paid my royalties through Paypal, I only have to wait a month to find out what has sold recently. (If I'd opted for a cheque, payments would be quarterly.) As mentioned, I had placed an ad in Radiojam to start last week, with a link to Amazon. I have to admit here that most of my sales are not from Amazon. Radiojam went out on Wednesday and over the course of the day, my Amazon sales ranking rose steadily from somewhere in the region of 250,000 to 2,000. I'm not the brightest person when it comes to maths (as those who have already read my book will know) but it surely means I've sold one or two here, doesn't it? John Haines, another long-time Lulu writer, says somewhere that a sale of one book can mean a jump of a thousand places sometimes. Is there a science to it, or is it just complete chaos? Does the ranking include only sales, or hits as well? Does anyone know? Unfortunately, despite another advert in Radiojam this week (and it will appear there for another 4 weeks) my Amazon rating continues to fall once again, and currently stands at 128,487. Hey ho!