Things do happen that fast. You are going to want to dose to 4 on ammonia and see it converted to nitrate in 24 hours. That's when you know you've developed enough of the beneficial bacteria.
As far as the salinity, did you mix the water first, or did you mix in the tank? It takes a good amount of time for all of the salt to fully dissolve and get into the water. So, if you tested the water shortly after mixing, the salinity could have continued to rise as the rest of the salt dissolved. Just a thought, as I did the same thing when I started out. To drop your salinity now, just siphon out some water and replace with RODI
. You're not too far off, so go slowly. Once you get it set, it will remain close to your desired level with the addition of RODI
to replace evaporation.