Hello and welcome to Just Answer.
I'm not sure I understand what you are asking. The car has to be driven to update the key. The mileage is not always exactly the same as the car. I've seen them be several miles off but it should be closer to the mileage when the car was shut off.
BMW Master technician
BMW S.T.E.P. graduate, 10 years BMW dealership experience
I would not take the mileage reading from the key as gospel. Like I said, They can be off as much as a few miles.
Modern BMW's are very difficult if not impossible to steal without a key. That seems a little fishy if all the keys are still in your possession.