Hi Kasey,
The better approach is definitely to get the data format right. This will enable you to great graphs/charts from the data in the future should you need to.
If however, you can't change the format (since you can't amend once the field is created and making a new field might be problematic), you could use the following text mode for the column in your report:
aggregator.displayformat=HTML
aggregator.function=SUM
aggregator.valueexpression=NUMBER({DE:FIELD NAME})
aggregator.valueformat=HTML
displayname=
linkedname=direct
namekey=FIELD NAME
querysort=DE:FIELD NAME
textmode=true
valueexpression=NUMBER({DE:FIELD NAME})
valuefield=FIELD NAME
valueformat=customDataLabelsAsString
This should SUM all of the values into your group header.
Best Regards,
Rich.