Need Advice on Hygrometer readings

[jimstep]

I am a neebee to the cigar world. I have recently purchased a humidor and additionally purchased a hygrometer so that I make sure I am within the tolerance range. From reading reviews, it has been suggested to calibrate the hygrometer, even the digital ones, like the one I have. So, I did the salt test. My results were 63%. The unit is suppose to have a 5% tolerance. This is 12%.

Is it normal to have such a large variance?

My concern it that the hygrometer reads 66% in the humidor. Does that mean the humidity is actually 78%???(66%+12%variance).