Are you looking for the Cl and Na contributions to your water when adding table salt? What do you hope to accomplish by adding table salt? Have you considered using CaCl? It's a much better salt for brewing. The Ca will help with the mash pH and you don't get the saltiness, or metallic sweetness that Na adds. CaCl does a fine job of enhancing sweetness as well.
but, to answer your question:
6 grams = 1 tsp and will add 624 ppm of Na to one gallon of water and 960 ppm of Cl to one gallon of water.