Cadillac Repair: speedometer reset, digital speedometer, federal law states

Question
I recently had to replace the digital speedometer in my 99 Devlle but the good one is different in miles than the old one although  it works great.  How can I reset this one to the mileage of the vehicle?

Answer
You CAN'T reset it.

Federal law states: You can either take it to a speedometer test facility where the police departments get their patrol cars speedometers calibrated and they will set it to the actual mileage as the old one.

                               OR

Have the speedometer set to ZERO and attach a label with the actual mileage on the old display on the drivers door frame with the actual mileage and the DATE that you replaced it.