MCF8316AEVM: oscilloscope timing incorrect

Tool/software:

1. With the motor spinning at 50%, I’ve simultaneously started a stopwatch and started the chart, I stopped the motor at 15s on the stopwatch and the chart soon afterwards the stop time on the datalog was <12s
2. With the motor spinning at 10%, I’ve simultaneously started a stopwatch and started the chart, I increased speed by 10% every 10s on the stop watch until 80% and stopped after another 10s the 80s on the stopwatch when I stopped the motor corresponds to <65s on the data log and the steps are uniform on the chart