Okay, here's how I do the math:
First line: 4.5 x 1376 in length, then fold in half and sew together to get:
Second 9 x 688
Third 18 x 344
Fourth 36 x 172
Fifth 72 x 86
Then, when you add your 30" of borders, you'll have 102" by 116".
The 116" may vary but the 102" won't, or in other words, the 72" will definitely be what you get if you fold to the fifth time, but the 86" could vary depending on how many strips you use. If you figure one charm roll plus one square is 43.5 plus 4.5 for a total of 48", that's the length of each charm plus square unit. If you divide 1376" by 48", you get an uneven number of units needed – 28-2/3 strips. If you cut one charm roll plus square unit to 32 inches (2/3 of a 48" unit) as a starting piece, you should come out to the dimensions I said. You will need 29 charm rolls and 29 squares.
If this doesn't make sense, let me know and I will try to come up with a diagram for you...