The horizontal white strip provides 1/4" seam allowance for connecting the bodice (top) with the skirt (bottom).
The white "fireworks" are positioned so that the vertical center of this fabric swatch equals the vertical center of Kimber's front, and a closure for the dress (i.e. zipper, velcro, snaps, or hooks/eyes) can be placed down the center back.
Please message me with any questions about this fabric.
A fashion drawing of Kimber's dress can be found on Pranceatron's Jem Cartoon Wardrobe site.