Well, after looking over my big Brother, I don't have a right needle setting. That was a surprise, but since I have never looked for it and I bought my machine in 2007, I haven't missed it. So, I set the needle as center, then moved it to the right as 6.0mm and this gives me the left 1/4 inch at the inside of the left prong. By the way, I don't sew with the single needle plate, I always use my zigzag opening because I am always moving the needle when I am piecing.
mckwilter, what needle setting are you using - center?