The option production totals came from plant build records. The record for each car listed, by internal code, how the car was configured in production. It is not the same as order configuration.
The only known surviving '60s build records are for cars shipped to Canada. A long time ago, GM Canada would send a copy of the page your car was on in addition to the letter. They stopped the practice many years ago, possibly because key codes were displayed. In the two records shown, the 1st car was built only with J50 Power Brakes. The next car, a Camaro SS, lists J50 and J52 even though it was included with Camaro SS equipment [Z27AA5].
When all this was tallied at the end of production, 82,890 cars were built with J50, 67,231 were built with both. The 67,231 total includes 34,932 Camaro SS.
Sure would be nice to have the complete, original report.