I think each dog is individual and over time, your mommy instinct will tell you if your pup is being fed enough or too little.
My breeder told me to free feed Snoops when I got him, and observe how much he eats and when he eats. This was at 3 months old. I suppose this is because hypoglycemia is a big deal in small breeds. I fed him 3x daily (1/4 cup each meal) up until about 7 months old, almost 8 months. I've only just cut back his food intake to 2x daily. Keep in mind, Snoops is a tiny toy (not sure if it would be the same for a spoo)
Lately tho, I've noticed that he gets extremely hungry around mid afternoon so I think I am going to start giving him an extra helping (1/8 cup) at that time to hold him over til dinner.