In the Copy and Import functions, what does the Overwrite Data check box do?

When you copy or import data there is a check box on the form labeled Overwrite Data.

If checked, the new target category data will replace any existing sub-category data in the target category across all periods and cost centers.

If unchecked, the new target category data will be added as another subcategory line item across all periods and cost centers, thus adding the new data to the old.