Calibrating Hygrometer

Recently I picked up a small 20 count humidor from Cigars International that came with beads, cutter, lighter and a couple of sticks. I went to Wally World and picked up an hygrometer (thought it was an acurite, but I just looked and its a springfield something or other). Anyway, its been sitting in the humidor for over a week and it never showed above 50%. I am in the process of doing the calibration test with a cap full of salt and distilled water in a ziplock bag. Its been in the bag for over 12 hours and never got above 54%.
What should I do? Get another one or is it really going to show almost 20% off (showing 54% when its really 75%)?

TIA