Xikar Rectangular Hygrometer

I am new here.

Hopefully someone can give me a more detailed description of calibrating an Xikar Hygrometer. I am in the process of calibrating the hygrometer according to Xikar's instructions. I mixed the salt and DOUBLE BAGGED the hygrometer in two heavy duty zip lock bags. Is this sufficient? Does the ambient temperature have anything to do with the results? The instructions say 4 hours is enough, should I wait longer?

Thanks in advance for any help.

Zman