I assume its just a angle finder no? So turn it on and place the level on a roof or something and it will tell you the pitch.
It props have memory in it to save the angles you got! Also a button for calibration to reset it to zero! Props a button to turn on a beep sound so you can place your level on the surface and you dont need to look at the level as it will beep at you when it hits the level mark or degree you have entered into it.
I am just making assumptions on how most digital levels work and so I think how this festool will work
JMB