What's written on the pack, in my opinion, should be ignored. I was obsessed with my LO only having the amount of formula it said on the pack, but then she got really hungry, and it was heart-wrenching to watch her scream for more milk and me not be "allowed" to give it. I would also give her a feed, and she would be hungry again within 3 hours. How can you refuse to feed them for another 2 hours if they're already hungry?
Eventually we started demand feeding, which is esentially giving them a bottle whenever they're hungry. She would start sleeping through the night, so the feeds she had during the day totalled what the guidelines were on the pack anyway. She woudl have less bottles (because no feeds during the night), but bigger bottles.
Then she decreased, and would only eat half of the guideline amount. But she's weighed regularly and she's always been in the 50th centile, and a happy baby, so everyone's happy she's getting what she needs.
She's recently (over the past week) started taking more, but still only 2/3 of what she "should" be taking. Again, she's healthy. In the States they don't have guideline amounts on their formula packs; the mums just give what their baby wants. A baby doesn't understand the concept of greed, and will only cry for a feed when it needs it.