Radiators in the winter and air conditioners in the summer dry out the air in your room. The weatherman gives you the outdoor humidity. Your DAMPIT humidity-indicator shows the indoor humidity and also tells you what humidity level will best protect your instrument from cracking or coming unglued. The best humidity level is 40-50%. Note that the color segments on your humidity indicator change from pink to blue. If the segments are all pink the humidity is over 50% — if all blue under 10%. Match the segment color with the color bloc on the right.
Another way to read the humidity is to note the greyish color between the pink and the blue.