Xikar Dig Hygro

Any ideas on this? I just got the unit a week ago...did the salt test with it and once ready (after 24 hours) pressed the callibrate button and it went to 75%....put it in humi and the reading was high...salt tested again and re-callibrated, put it in humi again, reading high.....salt tested a 3rd time, re-callibrated and left it in ziplock bad and held constantly at 75%....thought I had it, put it in humi and reads high again...so I put in ziplock with cap of salt, dampened and after 1.5 hours it is reading 9% high...this is fine I can minus 9% off whatever readings Im getting but why is this not accurate? I have 65% beads in all humis and the beads actually look like they need some distilled....getting tired of all this work...