Hi Mauro,
One unfortunately never knows without the cars service documents from the start since as you know our odometer turns over to zero after 99,999 KM or Miles.
I purchased a 1987 BMW is new in 1987 and we managed to put over 400,000 KM on that car. My daughter had her for 10 years and just sold her to a BMW Mechanic. Now this car had all the records and the odometer does not turn over after 99,999 to zero.
So yours could be 109,000, 209,000 one just don't know. Be happy if you have matching numbers and she runs well. There may be a way once you disassemble the engine and look at wear and tear what the true mileage would be, that as you can imagine is expensive and something I'm sure you don't want to do.
Enjoy the car.
Dieter