Don't throw darts at me if I am wrong, but I think I understand. Decide on the size of the outside squares. Then double it and subtract 1/2" to find the length of the folded goose piece.
For example 4" squares
4 + 4 - 1/2" = 7 1/2, so the the goose is 4" x 7 1/2"
or
5" squares
5 + 5 - 1/2" = 9 1/2, so the goose is 5" x 9 1/2"
Clear as mud???