What is the A3 upgrade order when overbooked Y? I got one operational upgrade but no idea if it was due to A3*G or simply being last person to check-in.

Flying on a flight overbooked in Y in 2 days and will be checked through, first leg is not overbooked. Will this reduce my chances of an upgrade as I'll be one of the first to checkin instead of last? There is still J (even J award) availability.