In the EBC 4.12 method for measuring the diastatic activity of malt, titration with sodium thiosulfate is used at the final step. It is stated that the remaining (unreacted) iodine should be titrated with thiosulfate. My question is: Why does a higher consumption of sodium thiosulfate indicate a greater amount of unreacted iodine and, consequently, lower enzymatic activity? Explain the titration step, please!