I would have put this down to an error in my spreadsheet, except that for the live game, both the old and new version, my spreadsheet continues to calculate the CpS precisely, correct to at least 4 significant digits. On the beta, however, my estimate is low by about 2%.
The error is in the multiplier itself. This overall CpS multiplier is made up of seven components, however at the very beginning of the run, before purchasing anything, the error is still there. At this point there are only two components to the overall multiplier: the boost from kittens in the permanent upgrade slots, and the boost from the two heavenly cookie upgrades, Heavenly Cookies and Wrinkly Cookies, which each give 10%. None of the other multipliers are operational. Prestige upgrade does not apply, because the Heavenly Chip Secret, Heavenly Cookie Stand etc are not yet purchased. Hence it seems to imply that the error is in the calculation of one of these two multipliers, but I cannot for the life of me track the error down. Moreover, as I said, the calculations are perfect for the live game, which uses exactly the same spreadsheet as the beta game, leading me to think there is a difference in the actual beta game code from the live game code.
Has anyone else noticed this? A difference of 2% is not a game-changer, but it's still either an error in the code or an error in my spreadsheet, and I've discovered from working in IT that it's a good idea not to ignore small errors, because they can be a symptom of something more seriously wrong with the code. OK, no planes are going to fall out of the sky if Cookie Clicker falls over, it's not going to kill anyone, but it would still be nice to know the reason for the discrepancy.