Average realized spread
(9) Average realized spread means the share-weighted average of realized spreads for order executions calculated, for buy orders, as double the amount of difference between the execution price and the midpoint of the national best bid and national best offer five minutes after the time of order execution and, for sell orders, as double the amount of difference between the midpoint of the national best bid and national best offer five minutes after the time of order execution and the execution price; provided, however, that the midpoint of the final national best bid and national best offer disseminated for regular trading hours shall be used to calculate a realized spread if it is disseminated less than five minutes after the time of order execution.