Flashing mileage

Hi everyone,

I bought a 2004 Mini Cooper about 4 months and now the mileage flashes up when I turn the ignition on. It flashes with -38,000 which seems a bit alarming.

I know the previous owner did his own oil changes rather than taking it to an official dealer, could this be the reason it is flashing?

I also read that this could be linked to brake fluid change.

Any advice would be greatly appreciated!

Thanks