Yesterday, I used the Brewer's Friend android app (very convenient) to calculate amount of DME to use at bottling. Calculator said for 5.0 gallons at 70F to get 2.5 volumes CO2, use 7.5 oz. DME. Today, I looked at the calculator on the Brewer's Friend website and input the same numbers. The result was 6.5 oz. DME. Any ideas on why the difference?