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When you first sort, the sum will be shown as ABC in the columns. To change, this move the Number of Records,
which is located on the left side of the screen, to the Marks section. The Sum(NumbersofRecords) will now look like this - 
Click on the four dots to the left of it and chose the text option. Now the Sum(NumberofRecords) will look like this - 
When you are completed with all the adjustments that you want to make, the final document will look similar to this -
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