How does AA calculate mileage--I'm confused
Recently took at trip with the exact same segments and class of service outbound and inbound. The numbesr I'm posting are the base miles + bonus miles, I'm EXP):
OUTBOUND: GRR-ORD 132 miles
ORD-LHR 3795 miles
LHR-IST 2559 miles
RETURN: IST-LHR 800 miles
LHR-ORD 4389 miles
ORD-GRR 77 miles
Total miles outbound 6486, total miles return 5346--same exact routes.
Can anyone explain how these numbers are calculated?