What am i doing wrong???

[d'am]

Regarding the salt test, I can't imagine why it would hurt a hygrometer. I suspect that the manufacturer is worried about loose salt finding its way in your hygro and the subsequent warranty request.

That said, if you don't test either by salt or the boveda pack, you're in for a lot more headaches down the road. Your hygro's error will drift plus or minus over time.