Porsche Boxster Owner's Manual page 119

You can stop the stopwatch or measure
another intermediate time.
In order to start timing a new lap:
The "New lap?" selection appears for 5 seconds
after selection of "Intermediate time".
Select "New lap?" with the operating lever and
push the operating lever forwards.
The new lap is displayed on the on-board computer
and the PCM. Timing on the on-board computer and
on the PCM begins from zero. The stopwatch in the
instrument panel continues to show the total time.
The on-board computer display returns to the
"Stop timing/Intermediate time" selection
after a short period.
Controls, Instruments
117