The point of it...
This function allows you to see a total and basic statistics on each column of data, if the data are numerical.
How to do it
With a word-list, concordance or key-words list visible, choose the menu item View | Column Totals to switch column totals on or off.
Here we see column totals on a detailed consistency list based on Shakespeare's plays. The list itself is sorted by the Texts column: the top items are found in all 35 of the plays used for the list. In the case of Anthony and Cleopatra, A represents 1.28% of the words in that column, that is 1.28% of the words of the play Anthony and Cleopatra. In the case of ACT this is the highest percentage in its row (this word is used more in percentage terms in that play than in the others).
See also: save as Excel