You won't see it until after the trip.

When two or more people buy tickets together, the airline prices those tickets at the higher price. So for example if they had one seat left for $250 and a ton of seats at $300, if you booked two tickets, they would charge $300 each.

If a person came along to buy just one ticket, and they had a seat available for $250, they would sell that ticket for $250.

That's one explainiation for the difference.

In any case, they are pretty clear as to how long it will take:

Expect to receive your refund check approximately 6-8 weeks after your trip is complete. We'll mail it to the billing address for the credit card used to make the booking. You'll have 90 days from the date the check is issued to cash it.