Just look at those boardwalk margins at the top and bottom of that "guideline" pair. Now look at the top and bottom margins of the "356".
Look at these, too:
http://www.ebay.com/itm/nystamps-US-Sta ... 58946afa0aMe thinks I smell something rotten in Denmark (to mix metaphors).
By eBay calculations, 99.95% = 100%, so if you have fewer than 5 complaints per 10,000 transactions, you are a 100% seller. Neutral doesn't count against you anymore, so by offering a full refund, even refunding shipping, makes it possible to offer such things without damaging your feedback. And even if you do get more than 5 per 10,000, you would have to get more than 1 negative per hundred to get lower than a 99% rating!