I just bought one and ruined a recording tonight cause I didn't quite know how this thing operated, thanks for the info 
That's frustrating. I always try to test my new equipment at home before I take it out for the first time. I'll crank the stereo up high and record something. It doesn't tell you what settings you should go with, but it does familiarize you with the gear, gets you turning on the buttons, plugging in cables and stuff like that. It also gives you at least a little bit of feel for what you can get away with on settings because it can kinda tell you at least a little bit about how your setup will react to the sound pressure of at least your stereo system and then you can adjust from there for when you go out in the real world.
For example, if I hadn't done this one time in the past, I would have gotten into the field and discovered that my cables wouldn't even have fit because the XLRs weren't aligned right and the jacks on the recorder were too close together for the XLRs to fit properly. So I had to take the XLRs apart and change the orientation of the pins for the cables to fit.