More of a goof that was missed

In the scene where Sam Diamond and Tess are in the car going over Twains file, she says he was born in 1906. During the first meeting with Twain in the dining room he states that he is 76 and how he looks so young. This does not make any chronological sense, seeing as if he was truly that age, the movie would be set in 1982, much later than it was even released, and much later than the period setting of the movie overall