Thats because, I think, is an old model. See that link of product manuals or something like that, in past models should appear the manual for this item.
By the way.... Today I did my fist real ride after I installed it... and what I realized is that all the KM I did, was automaticly added to the odometer count.... so... is it for that use?... to track all the distance you do besides the day, and segment?.
well, post wat you know.
Thnx