You could add more, but there are only two ways to miss the gravity on an extract recipe: adding the wrong amount of water or not mixing it enough before taking the sample.
DME runs 36 points per pound per gallon. Four pounds is 144 points, so if you made a three gallon batch your OG would be 1.048. To have an OG of 1.057 would have meant a 2.5 gallon batch.
Dissolve a pound of extract in a pint of boiling water, let it cool and add.
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