For an individual order, Price Improvement Dollars refers to the difference between the limit price on the order and the auction clearing price (i.e. the price at which the order is filled) for the given security, times the quantity filled. For an Expressive Order to buy and/or sell multiple securities simultaneously, price improvement refers to differences in limit prices and clearing prices for each respective security, summed across all securities times the quantities filled. Aggregate Price Improvement represents the sum of Price Improvement Dollars across all eligible orders (across all securities) under consideration for a given auction.