Looking at the US spreadsheet, the formula in cell E30 should be roughly (C27*322 + G27*363)/C23. In other words, the factors for converting chalk and baking soda to bicarb are both wrong. Correcting E30 should result in L30 giving the proper result.
The "corrected" equation assumes that the chalk and baking soda fully dissolve. However, Kai points out earlier that the chalk does not fully dissolve and thus the original factor of 158.4 rather than 322 might not be wrong as an empiricism. However, it is unclear why the discrepancy for the baking soda factor. Baking soda dissolves well; the solubility of baking soda is 100 g/l at 20 C vs. .015 g/l for chalk at 25 C per wikipedia.