Sorry about that spelling..
The manual said, tires will slightly increase in diameter as vehicle speed increases. To minimize this error, ride at a average speed during calibration.
"Approximately 45 MPH for most vehicles".
Tire slippage. Minimize this error by not breaking traction.
Speedometer accuracy depends on the accuracy of the measured two mile distance.
The speedometer calibration is based upon the number of pulses that the speedometer sensor generates in a two mile distance. This value is dependant upon several factors such as tire size, front and rear pulley size, sensor gear in the transmission and final drive ratios in the transmission.
Pulse count is set at the factory and cannot be changed unless a field calibration is performed
Dogvet can surely add or correct any info here.