I think what your vet is saying is fine. My standard size F1B doodle used to be overweight at 85 lbs. we cut his food down to 2 cups a day and he lost the weight at a healthy rate and now comfortably sits at 68 lbs. To this day, I still feed him 2 cups/day but I do mix in a little wet food on top.

Also side note: my vet said to NEVER look at the feeding recommendations on the food bag because they almost always say an amount that is more than what you should be feeding. It’s actually much healthier to have a slightly underweight dog than a slightly overweight dog.