The trick to this is that the rating system used is 0 - 100, not the 0 - 10 that we so often use. If someone tells me that an item I am interested in purchasing is rated as a number, then I make certain to ask what their rating is based on (0-5, 0-10, 0-100 or whatever).
Never assume that everyone uses the same rating system. There are those that are after your money and if they sell you something rated as an 8 make sure that it is rated as 8/10.