TFA HiTrax Tip Handbuch Seite 24

10.0 To Use the Chronograph Mode
In 'Zero' Display, press the [start/stop] button once to start the
counting. When it is counting, press the [start/stop] button once
again to stop the counting, and the elapsed time of which the
chronograph is counting will appear.
When the elapsed time is displaying, repeat the above mentioned
key operations to get the accumulative elapsed time or press the
[reset] button to reset the chronograph (ready for a new counting).
The maximum counting range of the chronograph is 99 hours, 59
minutes and 59.99 seconds.