the specification limit for the length of a type of glass fiber is [18.3, 23.7]. The average length of your manufacturing process is 21, but you only have Cp=0.9. For glass gibers longer than USL, rework can be done to cut it short, so that it can be used in the next assembly stage. However, if it is shorter than LSL, it has to be scrapped and becomes waste in the process.