The line that serves as an example of an anecdote from Utopia is:
C: I never saw a clearer instance of the opposite impressions that different customs make on people than I observed in the ambassadors of the Anemolians, who came to Amaurot when I was there.
This line indicates that the speaker is about to recount a specific event regarding the ambassadors, which supports the larger point about how different customs can lead to differing impressions and valuations among people.