The 3 2 1 formula is based on a 3 part nutrient system. The 3 2 1 is the ratio you use these (3) parts at; So if you use 6 total cups of nutrient, (3) will be made up of Part A, (2) will be made up of Part B and (1) will be made up of Part C. The 3 2 1 is not indicative of the NPK ratio.