Not that many. They can do it at like 2-3, with 1/1000000th the training set, at least words wise.
For comparison GPT has like 1TB of text, and they're hundreds of thousands of books, articles, wikipedia, and so on. So already 3 orders of magnitude more.
And of course the "16 hours x 150 words per minute x 3 years" is totally off by a few orders of magnitude itself.