I don't know the equivalent of campden tablets to potassium metabisulfite but if 1 tablet equals 1/4 tsp of meta then that would mean your recipe calls for 1 1/2 tsp of meta? That would be fine for 30 gals but if you are making 5 gals it is way too much. How much wine are you making? Generally you add 1/4 tsp of meta per 5 gals to achieve around 50 ppm.