It's calculated from the best times of each times of the 54 levels in stats.txt ( Elma directory). Skipped levels mean 10 minutes extra. On Moposite total time isn't accepted unless all the internal levels are finished.
The total length of time for which the Trip Computer has been tracking your location, since the Trip Computer was last reset. This is always equal to Driving Time plus Stopped Time.
All time during the period being measured (at the rate of 24 hours per day, seven days per week.) Also equal to the sum of time spent in all six equipment time categories.