Alkalinity levels of 50 to 170 are the values generally recommended in the literature for Koi ponds.
Alkalinity is related to the buffering capacity, or pH stability of the pond.
The measured KH before the addition was 5 o dH or 89.5 ppm. After the addition the KH increased to 6.5 o dH or 116.4 ppm. In other words, the addition added 26.9 ppm of carbonate to the pond as measured. Remember that ppm has to use the same units, i.e., grams of baking soda to grams of water in the pond. So we added 300 g of baking soda to 7,500,000 g of pond water.