The Defined Percentage Row (DPR) is an optional field in the Line Definition which indicates that the line will be referenced in column formulas. For example, you can use a line value in the column formula that will calculate a percent of a total for a given period of data.
To use a Defined Percentage Row, you must first enter a code in the Code field for the row in the line set. Then, you will enter that Code value in the Defined Percentage Row (DPR) field in the Line Definition where the calculation rows will begin (usually the first row in the Line Definition). The Defined Percentage Row (DPR) which is referenced in the Line Definition’s DPR field will be in effect until you define another further down in the line set.
Next, you will create your calculation in the specific Column Definition’s Formula field. You must use the special formula characters (@DPR) in your Formula field to reference the line value. For example, the formula ([B]/@DPR), will use the Defined Percentage Row set in the Line Definition’s DPR field – referenced by this special formula character “DPR”. The value in the column used in the calculation is referenced by the Column Definition’s Code field label of “B”.
Lastly, when you run the report that has the Defined Percentage Row (DPR) components defined, the calculated column (in the above example, column B) will divide the numerator by the value in the referenced DPR row - in this instance to provide for a "Percent of Total" calculation.
Remember to define your Number Format settings as a percentage in the Column Definition to obtain the formatting you want for your report column.
For more information please see the DPR Topic in Prospero Help: Defined Percentage Row