I have that exact same pattern and I found that part confusing I almost did the same thing you did that minus 8 inches is after you cut the triangles look at the green and white diagram in the instructions,that paragraph of instructions is misleading at least to me, makes you think you should cut your fabric at 8 inches less then the size you want but that's not the case it took me a while to figure that out DUH! Me it is a very easy pattern hope you post a picture