I had confirmed biz class redemption on QF using asiamiles. Was able to use first leg on biz class but on return I was downgraded to Y class due to over booking.

I was given cash compensation and was told mileage difference will be refunded.

Just want to check if anyone knows how the refund should be computed / what am I entitled to?

Zone C booking -

RT J @ 80,000 miles
RT Y @ 45,000
OW J @ 45,000
OW Y @ 25,000

Thank you.