Ok,take a deeeeeeeep breathe and say "there is no hurry". Nothing good happens quickly in saltwater. If you are adding salt now youre at least a month from your first fish. Your tool while basic is fairly foolproof. Odds are, as long as the arm swings freely it will work. Its easy enough to check. Take a water sample and seriously overload.it with salt. If it works you know the package directions on the salt arent matching your setup, which is pretty likely.
As a safety, take a sample and your hydro to your lfs
. Have them test a corroborate the tools reading.