Fare Rules
Certain fares can be combined with other fares as stated in the fare rules. In this case, the fare was priced using 1/2 of the roundtrip 7-day advance purchase on the outbound, and 1/2 of the roundtrip 14-day purchase for the return. Both fares must have been combinable, requiring a roundtrip and you met the restrictions of each given the priced itin.