Wine making kits often include packets of components required to make a great wine. Typically, a packet containing potassium metabisulfite (creates sulfites in wine) is included for use during the stabilization and clearing process.
Levels of sulfites are measured in ppm (parts per million). Approximately 9 ppm of sulfites occur naturally in wine making. In the US, a wine must have less than 30 ppm for the label to state “No Sulfites”. Sulfite levels greater than 30 ppm requires the winery to include a “Contains Sulfites” statement on the wine label.
Most wine kits create finished wines with sulfite levels around 20-30 ppm. Many manufactures suggest adding an additional 1/4 tsp of potassium metabisulfite per six gallons (23 liters) of wine prior to bottling to raise the level of sulfites a bit more to help them age gracefully for a couple of years.
Commercial wines frequently contain free sulfite levels ranging around 75 ppm.