VDO programmable tachometer with hour meter

Does anyone know how to reset the hour meter reading to zero on this instrument? It was originally supplied by Jabiru as part of my Jab 5100 firewall forward kit for my RV9a, but having decided to change engine to a new Lycoming O320 D2G I would like to reset the hours to zero.
None of the VDO documents I can find on the web deal with this topic