Overall, TDS is not super important. It can be somewhat useful in detecting unusual problems. For example, if the meter showed an unusually high TDS reading that did not correspond to the known ionic components of the water, it would suggest that further investigation might be necessary to identify the unknown ions.
Unusually high TDS reading could come from such ions as phosphates, nitrates, sulfates, potassium, magnesium etc.
Note: 1,000 ppm TDS-442 is the same number of ions as 687 ppm NaCl. Therefore, if the Electrical conductivity were the same for the same number of ions, then 4350 ppm TDS-442 would convert to 2988 ppm NaCl.
*[edit]I was assuming that the ratios of sodium sulfate, sodium bicarbonate and sodium chloride were on a molar basis. However, now I think that they might be on a mass basis. If the ratios are on a mass basis, then 1,000 ppm TDS-442 will have the same number of ions as 725 ppm of sodium chloride (NaCl). Either way, the number is about the same, and the correct conversion is determined by the measured values of conductivity vs. the concentration. Also, the ions are not just sodium and chloride, so there will be some inaccuracy based on that.[end edit]
However, different ions conduct electricity differently, and you can't use a single conversion factor. The chart below shows that 4350 ppm TDS-442 converts to about 2850 ppm NaCl, which is about 655 ppm NaCl per 1,000 ppm TDS-442.
It would be helpful if you got a standard salt solution to use as a reference, such as 3,200 ppm GLX-CAL-SOL. You could use that to determine a TDS reading that would correspond to a proper salt concentration. It would also help determine what units your meter is reporting in.
Here is a conversion chart for TDS-442 to NaCl.
http://www.myronl.com/products/solutions.htm