Yes, you need to know where UV, visible and IR are positioned and the actual wavelengths. Look at some published spectra in Mees and James or here, that I have posted to see how they look. That is about the best I can say.
Mine is calibrated, and has 2 settings. One is visible and one is IR. If I don't use a UV filter, I get a UV harmonic at 700 nm. This harmonic vanishes with a UV filter and is one of the faults of these particular instruments.