Data items on Classic report layouts

If this property is used in conjunction with the GroupTotalFields Property, totals can be maintained for both the groups that are defined and all records that are output; if used by itself, TotalFields will maintain totals for all records.

Enter a comma-separated list of field names. The fields can be selected by clicking the AssistEdit button in the Value field of this property.

The totals are printed by placing controls that have the fields that are indicated in TotalFields as their source expressions in a Footer, GroupFooter, TransHeader, or TransFooter section of the data item.

Reference