If you change your radio in a later model Alfa Romeo, which has the CAN-BUS system in it, you may get an issue with your dash display where it displays the miles as 000000-do not worry, you’ve done nothing wrong, your car isn’t going to implode and you don’t need to see your dealer-unless you’re feeling flush;)
There is a known issue with the CAN system, which is what performs all the pre-start checks on your car when you turn the ignition on, having issue with your new radio as it is no longer the original CAN ready unit. The CAN system throws a hissy fit, shouts “mama mia” and then carries on as normal.
You may have these problems without changing your radio, another one of the little perks of Alfa ownership!
You can take the car to a dealer to have this re-set.