one bad feedback in 1216 and I go from 100% to 91%?

[cattsoho]

Do not understand how one bad feedback has such an impact on my rating.  The buyer did not even contact me for resolution.  I misized an item, would have happily refunded money for my error.

[jacbarcollectibles]

Your feedback percentage is calculated based on the feedback received in the last 12 months.  So since you only received 13 feedback in the last 12 months the calculation is correct.  Feedback older than 12 months does not factor into the percentage calculation.