To calculate the total IGT, simply add together all the race times. Use the following method:

• Use the times displayed after the race, since only those will show the milliseconds.
• If you retry any races, you must add the IGT displayed at the time the game was paused. Since that time will not show milliseconds, just add a 0 (.25 -> .250)
• If your game crashed during a race, add the last time that was visible before the crash.