Having check box selected is equivalent to Workflow Definitions Loader Upgrade mode.
Having check box deselected is equivalent to Workflow Definitions Loader Upload mode.
If the check box is not selected, you can save your edits only to protected objects that you have access to change, and cannot overwrite previously customized objects
If the check box is selected, you overwrite any protected objects that you have the ability (access) to modify, and also any previously customized objects.