I have had the same issue with the BB Kits. If you calculate the OG given the ingredients it is always lower than they state on the instructions.

Use these values in your calculations:

LME is 1.036 per pound per gallon use 36 points per gallon

DME/Sugar is 1.040 per pound per gallon use 40

Specialty Grain is 1.025 per pound per gallon use 25

To Calculate for the BB Imperial Pal Ale:

6.6 lb LME

1 lb of DME

1 lb of Sugar

Sp. Grains 1.75 lbs

LME 6.6 * 36 = 237.6

DME 1 * 40 = 40

Sugar 1*40 = 40

Grain 1.75 *25 = 43.75

-------------------------

Total = 361.35

Then Just divide by the final # of gallons which would be 5.

361.35 / 5 gallons = 72.27 or 1.072 OG

The Kit says it should be 1.081-1.085. The math says you should get 1.072. You got 1.070. I'd say you did good.

I hit the calculated value every time with the BB kits.