I don't doubt yer extremely fit but ..
I am 48, 181 cm tall and weigh about
13 stone (82 kg).
They just told me I have the fitness of a 37 year old!!!!
In reality I might be very slightly fitter than most folks my age - at best.
They didn't ask about diet.
They only gave over or under 30 mins daily exercise as options.
2 or 3 days exercise / nearly every day (about 4 walks per week for me this year isn't really covered).
The made a ridiculous estimate that max heartbeat was 182!!!! More like 160+ I'd guess.
I am stuck around 13 stone give or take a pound or two for the last few months.
Need to make sure I have less days where I am lazy and eat too much carbs plus eat a bit less.
Walked 17 miles on Monday and Tuesday so that is going well.
176 walks and over 1000 miles this year is OK. Usually like to do well over 200 walks plus per year and 1200+ miles.