Explosivo - Taken from their help section.
Members can affect each other's Feedback score by only one point per week. Each member may affect your score by one point per transaction. However, to make sure that repeat Feedback is calculated in the Feedback score, each transaction the member is leaving Feedback for must end in a separate week. For Feedback, eBay defines a week as Monday to Sunday
Positive Feedback - The percentage of positive ratings left by members in the last 12 months. This is calculated by dividing the number of positive ratings by the total number of ratings (positive + neutral + negative)
If a buyer leaves one neutral rating and one positive rating, it will affect the Feedback score by +1.
If a buyer leaves three negative ratings and one positive rating during the same week, the Feedback will affect the Feedback score by -1.
I think what ebay are trying to do is cut back on the number of positive feedbacks you can give and receive from one member in one week. Rather than start from fresh they have decided to backdate everyones feedback. I have gone from 97% down to 92% positive feedback.
Ebay is best served for buying rather than selling, personally I hate the bastards.