Downgrade compensation is a percentage of the fare (excluding government and airport taxes) in accordance with EU261 depending on the distance and I believe it is 30% for this route. If this isn’t a direct one-way booking or return booking, you’ll have to use the Mennens formula to calculate your compensation. Please see a calculation here: https://www.flyertalk.com/forum/26864509-post636.html

However, I suspect you may have a hard time getting this unless you have some kind of evidence as your boarding pass will have “Plus” written on it. SAS apparently hands out “compensation cards” when you’re downgraded, which they use for checking eligibility for downgrade compensation. In addition, as AY was the original carrier, SAS may try to send you to AY for compensation as SAS may not know what you paid for your ticket.

Definitely give it a try with downgrade compensation, but you’ll probably have to file it as “other matters” rather than downgrade compensation and you may be better off hoping for a gesture of goodwill rather than EU261 compensation as the amount probably will be very low. The link to claim compensation is here: https://www.flysas.com/en/customer-s...other-matters/