I new to this, so forgive me. I can't seem to find an explanation on the Amazon sales rank. I went from 90,797 to 134,104 to 278,087 yesterday. I'm guess that's where I fall in line with all of the books sold yesterday which would mean I sold a few early, then probably not much of anything else during the day??? I'm guessing this updates constantly where Barnes & Noble doesn't.
From what I understand...it takes only one sale to raise your rank from the miliions to something under a million. It looks like you didn't sell any yesterday but sold one maybe the day before if the ranking preceding the 90K rank was over a million.
I've also heard that anything under 100,000 is good, 100,000 to 200,000 is OK, anything less than 300,000 is uh-oh city. The thing to do is to track the number over time. Several months would be good.
The best thing the Amazon numbers are for, though, is as a way to eat your heart out. Just do your best and don't worry about that number. It really doesn't mean a lot.