A caution: I own about 8 of those exact same Acu-Rite hygrometers. They vary by as much as 8% each. That is to say, I put all eight next to one another on the kitchen table. I checked the next day, and they ranged from 1% to 8% RH different from one another. I did this a couple times in other rooms...the ones that were higher were always higher, lower always lower. And since there's not way to calibrate those types, I actually calculated an average and then put a sticker on each, like +3 to mean it is generally 3 degrees below the average of the eight.
Take them with a slight grain of salt. (and cannot calibrate these with salt). Some would say, well, 8% humidity off isn't much. Well, if it was reading 35% you'd like say, "eh, it's okay". If it read 27%, you'd take your uke in the shower room for a steam bath. lo;l