An authorized Ford dealer probaboy replaced the speedometer/odometer in your car with one from Ford parts, that explains the red "tenths" on the ododmeter. It isn't anything to get too excited about if you are buying the car to keep. They are more difficult to trade to a dealer because there is such scepticism surrounding "true mileage" on a car.
A guy I work with had his speed-o replaced by Ford dealer and his tenths are red. When his was replaced, the dealer corrected the new odometer to read the same mileage as the old one. He has the appropriate paperwork to prove the correct mileage on his vehicle.
Hope this helps.
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Scott93GT
1993 Mustang GT
Silver CC/Titanium Accent GT, Black Clothe interior.
5 speed, 3.08's, 3 chamber Flows, K&N, Hurst Competition Plus.
1991 F150 4x4 XLT Lariat
Six Stick Regular Cab LWB Tow Vehicle