Baby rice cereal?

[HondaRGurl]

Doctor put my son on baby rice cereal when he was 3 1/2 months old for iron problems. I went into the doctor for his 4 month appointment and doc told me i could give him more cereal now that he is probably more used to it. How much should i be feeding him. He doesnt really stop eating when he is full So how do i know how much to feed him? Well atleast he has never stopped eating for me before because he was full. I just always gave him 4 oz of formula and when it was gone that was it i made a couple spoon fulls of baby rice cereal and when it was gone that was it. So how do i know how much to give him. Sorry this might be a stupid question but im really not sure. And a first time mom with not much help. Thanks