Waist length is the measurement from one of your neck bones to your back waistline.  If you are short, your waist length may be shorter than the normal and you will need to adjust a fitted garment pattern.  This is done by making  a tuck to shorten the torso pieces just above the waistline.  As I've recommended before, test a new pattern for fit by cutting the torso pieces from muslin and sewing together to try on for fit.  Transfer the waistline marks with the other pattern marks so you can compare yours with the pattern's.  More next time...