Use this option to specify the number of variables in the secondary data set to process as a group. Successive groups of this size are used until all variables are processed.Tip : This option is available to save on memory usage. Specify a smaller number if the process is running out of memory.Tip : To change the scale of the slider, right-click on the slider and select from the pop-up menu. Change the upper and/or lower boundaries in the window that appears, to rescale the slider and click .