What Jerry is referring to is the number of feedbacks showing for given bidders, as per the screenshot below, which is from the auction in question. You can see that the winning bidder had no feedback, possibly implying that it's an e bay account set up specifically for shill bidding. Obviously there's no hard evidence to definitively prove it, but that is the suspicion. Conversely, the previous bidder had a feedback score of 250 implying that they were an established respectable e bayer.
The percentage of positive feedback is the total number of positive feedbacks given by buyers/total number of feedbacks, given to that seller. So if somebody had 1000 feedbacks, 999 of which were positive, and one negative, their positive feedback would indeed be 99.9%.