Short Run SPC is used in batch production when the runs of any one item are too short to run standard Statistical Process Control.
The basic idea is to measure the deviation from the standard size. For example if bars of varying diameter are machined the control charts would monitor the deviations from the target bar diameter, rather than the bar diameter.
The snag with this may be that the amount of variation may vary from part to part. One way of dealing with this is to use the ZmR chart in which the deviation from the target value is divided by the Standard Deviation.