These indicate the known reliability of the odometer readings. There are four types of odometer descriptions:
ACTUAL – The mileage reading is believed to be accurate and true.
EXEMPT – No code is required, by federal law.
NOT ACTUAL – The reading is not accurate or could not be ascertained. This may be due to a variety of reasons — the odometer might have been repaired, or the vehicle in question might have been stolen, among others.
EXCEEDS MECHANICAL LIMITS – The odometer was unable to measure mileage because it manually exceeded its capacity.