There is no prescribed ratio for a Johnson Su. Follow any recipe that you like. When I put in two thirds of spruce bark mulch this was the attempt to coat the thing with a thick layer of something that will not decay fast as an outer layer (I hope to get rid of that “Plastic lining” as ours are not UV stabilized and are brittle in one year which makes this a) a danger in terms of microplastics and b) an expensive adventure).