"We went to the cave and made the boy comfortable. We gave him some of our lunch, and he ate it with the air of a connoisseur - which, for a kid, he certainly was."
The fact that Johnny, a "kid," is described as having the "air of a connoisseur" is an understatement. This is because connoisseurs are known for their refined taste and discerning judgments, qualities not typically associated with a mischievous child. By using this term, Sam humorously minimizes the fact that Johnny is a handful, making the reader chuckle at the absurdity of the situation.
This understatement further sets up the comedic tension of the story, as it highlights the disparity between the kidnappers' expectations of a simple ransom and the reality of their captive's unruly behavior.