I also received my 8500 miles, however pax 2 (exact same flights during promo period) who also signed up for the campaign and had identical earning activity during the promo period only received 3500 miles. Cathay support insists the promo was only for 3500 miles. Very strange. The only difference was the sign-up date I believe. Pax 2 signed up Dec 6 and I signed up Nov 30. Did they reduce the offer for people who signed up in December or something?