Menu: Filters Winning Numbers History
StdDev
There's Summary Table at the History showing sums and/or differences for each past winning numbers draw. The last but one column in this table is labeled StdDev (Diffs) and it contains the standard deviation calculated for the difference value in all columns. You can see the corresponding chart at History Chart tab - select Show: Differences Chart, click button Options under the chart window and make sure the last row is checked in the Chart Options window.
Lower StdDev value means that the difference value in most columns will not be very high and it can be expected that there will more differences in the +/-10 range (the recommended value is 4 to 6 differences in the +10/-10 range) - see filter Winning Numbers History - Sums.
Higher StdDev value means that negative and positive differences in each column will be higher as well and the number of differences in the +10/-10 range will be lower.