Jim:
I don't think it's adjustable, but the hours aren't 'clock' hours with the ignition on like mechanical meters.
I have a 2305 that's two years older than my 3720 and it's got far fewer hours on the meter.
(Not really, the 3720 runs at a fast rate).
I've never checked the run rate but I think it goes faster when the engine is running at full RPM, etc. The one on my 2305 is just a dumb hour meter.
It probably makes more sense to track engine rotations, load, etc. but it's disturbing when you see hours go up so fast.
Anyway, your 3720 isn't weird, it's like all the 3x20 and 4x20 series with electronic hour meters.