You can switch to twice a day. I don't switch my dogs to adult or ALS until they're a year old but your breeder may switch earlier.
Comet's 8 months and getting about the same amount of food.
I wouldn't increase or decrease if he looks good. Go by your dog's appearance and feel, not the bag's suggestions. When you do switch foods, the kcals per cup of each food will be listed on the bag by the nutrition/ingredient labels. That's how you figure out how much of the new food to feed. It'll be a good baseline, but you may need to adjust based on your own individual dog and activity level.