If you do not quilt as closely as the pkg recommended what happens is-- the batting ( can) separate in the large areas, it then wads up and becomes balls of batting and empty areas in the spaces between quilting lines. This happens with laundering and use over time.
For future projects always read the pkg before purchase. There are many available battings that allow up to 10" between lines - like warm & natural which has a polyester scrim the batting is punched into which keeps the separation & migration from happening.