Molim vas jednu dinju means “One melon, please” – the first sentence that contains a number.
You are sitting in the limousine with the vase in the morning, the familiar molim vas. This limousine comes gliding up every morning in an instant: “every” and “in an instant” give you jednu. And who brings the melon? A servant, and a very young one – servant (Diener in German) and young give you dinju.
Note that “one” is not jedan here but jednu: the ending depends on the word that follows.