Originally Posted by Jules
the cover is 400x597
I think Creator may be looking for 600 wide by 800 high, but I suggest ignoring the warning about the cover. 400x597 should definitely big enough, as you can confirm by looking at the ebook with Windows MobiPocket Reader. If you actually use 600x800, it will be rescaled to a smaller size on the Kindle (and probably the Gen3) anyway.