Most of the time that you sell two identical certificates at your auction, they will be for the same price. Though there may be a scenario where the certificates sell at different prices. For example, your silent auction rules may dictate you accept the top two bids. When reporting the winning bid amounts in TravelPledge, however, there is only one field to specify how much it sold for.
In this case, enter the average of the winning bids. Though, if a winning bid exceeds the retail value, input the retail value into your calculation of the average instead of the winning bid. This will ensure your cause keeps 100% of winning bid amounts above retail value.