hydo force 1:4 16 mean

What is 1:4 16. No tip? Is it 1gal output takes 4 gals out solution tank, and is equal to 16oz a gal. 2nd? When use of acid wash injection- what ratio should it be- i will be using the hydro for chem injection by adding a needle valve into a 10 chem tank i can adjust my flow and inline...