Stitch density.

The distance between neighbouring rows of stitches in a fill or satin column, which decides how many stitches cover an area and whether the fabric shows through. A smaller number is denser. Coats puts the cost on it: an area sewn at 0.55 mm uses 20% fewer stitches than the same area at 0.40 mm, and underlay plus a cover fill uses fewer stitches than cover stitching alone. Both ends fail. Coats warns that density set too high causes thread breaks and density too low leaves gaps where the fabric colour shows through. Wilcom works an example of a 4 mm satin column at 0.4 mm spacing and notes that stitches bunched on the inside of a curve break thread too. It is a digitising setting, so the seller does not type it in, but a design shrunk after digitising keeps its stitch count in a smaller area and ends up far denser than intended. Resize the source art and have it redigitised, rather than scaling the stitch file.