Faria tach/hour

[hperros]

Has anybody installed the FARIA BEEDE 32834 Euro Tachometer with Hourmeter (4000 RPM) Diesel - 4"". I thought I will give it a try before I buy the $350 tach. (As long as I do not install it, I can return it). It looks straightforward, but I am confused with the white setting button (1-6). It is currently set at 3. What is the correct value???