Actually, I think you were the beneficiary of great fortune via the upgrade - you probably should have only earned 5,174 miles, given one generally earns miles at the originally booked rate (upgrades don;t count.)
And as shown on
this aa.com page, BA K, L, M, N, O and G, Q, S, V fare classes only earn 25% of miles flown. On BA "very cheap tickets" mean "very low miles".