Beth Blauer and Dr. Jennifer Nuzzo, two key members of the Johns Hopkins team that is tracking every confirmed coronavirus case, tell Brian Stelter how they do it, what the numbers do and don't reveal, and why people can have confidence in the data, even though it is incomplete. With regards to the death toll, "we may see that the true number is actually larger than what's been reported," Nuzzo says, "not the other way around."