The observed performance section tells you the actual number of parts per million located beyond the specification limits.

·    PPM < LSL - number of parts per million (PPM) that have measurements less than the lower specification limit.

·    PPM > USL - number of parts per million (PPM) that have measurements greater than the upper specification limit.

·    PPM Total - number of parts per million (PPM) that have measurements beyond the specification limits. PPM Total is the sum of PPM < LSL and PPM > USL.

For the piston data, all measurements are located inside the specification interval, so all three PPMs are zero.