Hello- I just calibrated my current thermometer/hygrometer with the salt method. I've used it before with some success, then the hygrometer became unreliable. Anyway, I just calibrated a new one of a different brand. When you are aiming for 75 humidity, and you get 80 or 70, it's no big deal to add/subtract the difference and not the difference. However-THIS one shows 63 percent humidity after the salt. Do you think it's safe for me to just subtract 12 from the humidity that it shows when in use/ Or is that way beyond fixable? Hope I'm making sense. Thanks!