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Yes, 1/4th cup dry equal 150 calories per 1 cup of water. 

My morning steel-cut oats when I make it is 1/2 cup dry put into 2 cups of boiling water, and then I simmer it for 12 minutes.  That is 300 calories total, including the cooked oats and the water.

So if I understand your question, 1 cup of dry oats cooked in 4 cups of water would be 600 calories; but if you ate 1/4th of that, it would, indeed, be 150 calories.