A typical meal at the breast would be 2 or 3 oz, maybe 4, maybe 1 - depending on the feeding. But definitely not 6 oz! Keep in mind that the pattern of meals for breastfeeding is very different from formula feeding. Babies have a tendency to chug away at the bottle, so a formula-fed baby will often evolve into a pattern of larger, less frequent meals. Whereas a breastfed baby at the breast will have frequent, small meals; and you want to mimic that with the bottle as well to stay on track. Just because baby WILL drink a big bottle, does not mean she NEEDS a big bottle.
Here are some useful links on bottle-feeding the breastfed baby: