In recombination in bacteriophage genetics experiment, instead of the mixed T4 rII phage strains being placed in a test tube containing KCN (potassium cyanide), the mixture is diluted 100 fold in 9.9mL of nutrient broth. What is the purpose of this dilution?

Note: I am referring to step 2 in the picture below, KCN was not added however and I am asking why did we dilute it 100 fold in nutrient broth anyway.