What does no stitch mean in a graph

In order to keep a graph or chart square (or rectangular) “no stitch” is put into some rows. Perhaps you knit 2 together in the previous row, so there’s actually a stitch missing. Just skip that space and go on to the next direction or stitch.

It means “there’s no stitch on your needle for this box so ignore the box” and skip over it to the next box.