+1 2xai....if it's empty, go ahead and add enough rodi or distilled until it's the right level. If you have livestock, you shouldn't lower it too fast, although, fish can usually handle a quick drop in salinity (inverts and corals won't though). Raising salinity rapidly is harder for them to handle.
What are you using to check salinity? Refractometers are more reliable than the swing arm testers.
Also, make sure you're using rodi or distilled. Filtered water is not filtered enough for our tanks.