I've mentioned before that Amazon likes the long view... look how long it took from their opening before they initially became profitable. If they're planning on selling books digitally, you can bet they're not taking this trouble just to fold it next week. They're looking at the decade-long picture.
The percentage numbers are, yes, vague, could be decrypted in any number of ways. Again, they don't mean much, because we're still so early in the long view.