It does so by the "number" that the Hi and Lo are at. So in your case if the setting are maxxed out and can't give any more, then the computer program read this as a lean condition and can indicate so. So once you get used to seeing where normal numbers run, then you can start to tell when something is amiss. Same as if all of a sudden you have to tune two and a half turns out from normally one turn out, then you know something is wrong what you will have to find out, same as if reading the report.
So really, don't try and over think this thing because it's auto tune, it's still a saw, just whom or what is doing the tuning is the only real difference. At the end of the day a person has to get in there and find out what's going on. At least that's my take and experience with them. The internet however, it's all snake heads and chicken bones up in there...