Not a dumb question at all!!! I wondered the same when we were thickening bottles for reflux. I would probably count the pre-thickened formula as the ml total, although the extra cereal will help him with reflux and extra nutrients. We always had to feed small amounts throughout the day due to reflux pain, but if your little guy seems to be crying for more, maybe just go based on his cues? That's great that he seems to have an appetite.
Hang in there! GERD stinks... :wink: