I noticed you used 10 oz of 15% Alpha hop to get 178 IBU. How did you calculate that? My calculations show IBU should be 10 oz * .03 (percent utilization) * 0.15 (Alpha Units) * 7489 (standard calcuation value from Desiging Great Beers) / 10gallons * 1.412 corrected gravity. I get 475.94. Help...