I make my own with the SilverGen CS maker and find 10ppm works best. For store bought I go as high as 20ppm.
At 10ppm properly made CS is safe to probably drink by the gallons (though it would never be necessary). And unlike Antibiotics , germs and bacteria don't develop immunities to silver. So it's always good to have some on hand in case of emergency for the odd plague that may come your way. Or those times Antibiotics aren't working, or better yet to get off of Antibiotics completely (as I've done).