Porsche Boxster Owner's Manual page 116

The timing can be continued or reset to zero.
Note
PCM: After timing has been stopped, a prompt
asking whether the time is to be stored appears on
the PCM.
114
Controls, Instruments
Continue timing
After timing has been stopped, the on-board
computer display changes to the "Continue/Reset"
selection.
Push operating lever forward. The stopwatch
displays continue the timing.
The on-board computer display returns to the "Stop
timing/Intermediate time" selection. You can stop
the stopwatch or measure an intermediate time.