I think you might have looked at the wrong statistic when googling this. According to this site[0] (which is one of the first hits for "computer science graduates per year"), there are 2 million computer science people in the workforce _in total_, which seems far more realistic. Actual number of graduates per year seems to be 65000.

With your numbers (assuming linear growth) after those 40 years, about one third of the total US workforce would now be CS graduates.

[0]: https://datausa.io/profile/cip/computer-science-110701