In ecomdash the override value can be used to hard code a specific field value instead of having it read off of your spreadsheet. The override header is just for your reference to understand and remember why you set the value to be hard coded instead of dynamic.
If you want a different value to show, you can set the override value. If you want to blank out a value across all your products, you can upload an import format with fields and override those entirely.
**NOTE: The override header can only be applied to the export process**