Presumably someone asked him "when did this all start?", and he said "when I was, I think, 16? -- Louisiana passed this act and I...", and he didn't stop to cal

Presumably someone asked him "when did this all start?", and he said "when I was, I think, 16? -- Louisiana passed this act and I...", and he didn't stop to calculate it carefully. And it looked about right, and if he was off by one it's completely irrelevant, so quite rightly no one put any thought into making absolutely sure that the numbers were exactly right.