Scooterotica

ive been using this little cheap n cheerful little rev counter for some time now,its aparantly its for use on agricultural machinery...displays obviously revs and run time so i guess maintenance is sceduled by this.....unfortunatly its now telling me to lube my combine harvester and change the oil on my tractor after todays rideout
does anyone who uses one of these know how to reset them?

I use one and this happend to me, just leave it be and after a while it will re-set itself, bloody annoying though.