How do we know Jonathan's fear of dogs lessens at the hotel?

The dog is humping the table, which has caused one of Jonathan's two potatoes to fall on the very dirty floor. There is a tense moment. Finally Grandfather picks up the potato, cuts it in four, and gives a piece to each of the men and to the dog. He eats some of his piece first and tells Jonathan, "Welcome to Ukraine." After Alex translates it, all three of them laugh, and Alex perceives that each of them is laughing for his own reason.