In These multiples of the standard deviation, enter one or more values to display additional standard deviation lines on your control chart.
You can specify a lower bound and an upper bound for the control limits. If the calculated control limit is farther from the center line than the value that you specify, Minitab displays the bound instead of the control limit. Minitab labels the lower bound as LB and the upper bound as UB.
Upper bounds and lower bounds do not affect the calculations for any of the tests for special causes.