Thank you so far. I am building some kind of data logger currently. I used two digits for temperature, pressure, heading and acceleration now (seemed the range where it may be stable) and 3 digits for analog pins (just because it returns them).
For light i noticed, that daylight is in the range of 21000 (currently) while artificial light gave me 80. Not sure if the readings are really comparable or if there is some dependence on the spectra as well.