Unless I am mistaken, for domestic flight, the “reference” mileage is not 500 but 400 for some years now. But I know FB website still mentions a minimum reference earning of 500 miles, but this is wrong and misleading. If you use the calculator, it displays correctly 400. And all my recent domestic flights booked in full flex fares earned only 400 status/award miles (+ 400 status bonus award miles as a Platinum member).