The solution doesn't restrict the number of rides during daytime to the available demand. The total demand during daytime is 8.4 million and the daytime capacity is13.787.000 rides per year. The solution assumes that all the daytime capacity will be sold...
If we cap the daytime trips to the demand, the total revenue drops to $227,6 M per year and the total profit to -$13.7M in Y1 (with a negative ROI) changing the conclusion of the case.