What do the numbers in fertilizers mean? You need to remember the phrase “up, down and all around”. The first number is for the ‘up’; for green growth in lawns and/or plants. The middle number is phosphorus, that’s for strong roots, that’s the ‘down’. And the end number is potassium, which is for general health. That’s the ‘all-around’. So there it is, the “up, down, all around” of fertilizer.