Calculated in Death discussion

The book is quite interesting, but I did not entirely understand this excerpt: "Okay, John Smith from Albuquerque, too bad about that shuttle crash. Follow the green line to Orientation. And what if two John Smiths from Albuquerque happened to be in the same crash? It could happen." - What does it mean? What is "follow green line to Orientation?" About what shuttle crassh the author speaks? Who is John Smith? Can somebody help me? I shall be very grateful. Jonas