Justin listened closely to Spartan's instructions, then, "Yes sir. Got it. Observe, report and intervene only if they're getting in over their heads."
The 'getting in over their heads' part was probably a given based on what he had observed earlier. Of that Justin was certain.
The fact remained, however, that he had been given a considerable responsibility by the King of War and he was going to strive his best to meet the challenge.