How it is calculated
Time follows the clock in your browser, and nothing is sent to a server. A lap is the stretch since the previous mark, and the total at that moment is written beside it. The fastest lap and the slowest are marked once there is more than one lap.
Lap = total time now − total time of the previous lap
Example
Start, a lap of 12,40 s, then another of 11,05 s. The list shows two laps and the total. The PDF repeats that same table.
Questions
Can a lap be recorded while paused?
No. A lap is stored only while the stopwatch is running. While paused, the left button clears everything.
Does the PDF save the current run?
Yes. The file stores the total at the moment you tap, and a lap table: number, lap time, and total.
Does the phone screen turn off?
While the clock is running, the page asks the screen not to sleep. If the system refuses, the stopwatch still keeps time in the background of the tab.