It depends - so, are you feeding the 1/2 cup only in the morning right now? I feed 2x per day, bc unless you're strict prey model - I just don't think it's good for dogs to be eating 1x per day
. As for proper amounts, the guideline is good - but you can also use your dog's weight and condition as a good guide. Feeling the ribs is always good - as in, they should feel "just right" - not too prominent, not too buried.