Why not add 4.00 grams of kosher salt to 1 liter distilled water and use that as a 4,000 ppm NaCl standard solution. Dilute it as needed.
Also, for the Taylor salt test I find it easier to use a 20 mL sample, 2 drops of R-0630, then titrate. Each drop of titrant is worth 100 ppm NaCl, but the endpoint is easier to reach without going over (which is quite easy to do with this kit, you want salmon color, not brick (brick is the color you get when you mix 1 drop R-0630 and 1 drop R-0718).
Also, there is the salt content (NaCl) and the conductivity of the solution (which is anything added to the water that increases its ability to conduct electricity). The unit looks at that while the Taylor measures NaCl.