[Timer Start] When the timer shows 0.07, the edge of Course 81 is not yet red. This means the timer starts at least 0.07 seconds faster.

[Timer Stop] Timing ends when the pop-up after course 90 is visible at the bottom of the screen. At that time, the timer shows 1:46.59.

1:46.59 - 0.07 = 1:46.52, and rounding it, I got 1:46.5