The center square will determine what the other measurements are. I drew the block in EQ and it does show that the strips are going to be wonky 8th sizes. A different way to do this block would be to cut the strips going away from the center as a solid piece of the white. Then applique the center strip to the set. A bit more to do, but the wonky sizes go away. The white background would be the same width as the center block and you will determine what size the center strip would be rather than the pattern. Maybe a bit complicated if you are a beginner, but might be worth a try. FYI...I'm not good with 8ths either.