I think this is on topic for Science of Cooking - he makes specific adjustments to the standard cookie recipe to accommodate the added moisture from the sourdough discard. These are also the best cookies I've ever eaten, one of the few recipes I follow exactly, and we make them all the time, a double batch.

One adjustment, actually - I use slightly less chocolate chips, but no adjustments to the dough, it's perfect. Browning the butter always results in the same reduction in weight that is calculated in the recipe, even. Every time, I am amazed.