Tell your baby I meant no offense.
My dog is a fatty and and I tell her that all the time.
Those feeding guidelines are just that - guidelines. And much depends on brand too. I have never fed kitten food until just recently, and never to kittens over a few months old. I truly believe all these different formulas are unnecessary and are money-makers for dry food manufacturers - "Indoor formula" is a good example.
I feed primarily canned and believe it's better than any dry, which contains ingredients cats cannot use, like carbohydrates and grains.
If your kittens aren't fat then don't change anything.