Let's look in a little more detail at what this means.
The correspondence between the COBOL Entry Point fields and interface fields is set up when you do the drag-and-drop. If you right-click an elementary interface field, such as lnk_file_status, and click Mapping, you see a dialog box showing the COBOL Entry point field associated with it. This correspondence is not affected by the names or order of interface fields. You can use the dialog box to alter the mapping if you want.
In the messages passed between the service and a client, the interface fields are identified by keywords. Their names in the Interface Fields pane are used as the keywords. Nevertheless, their order in the Interface Fields pane is the order in which they are seen by a client, so it is good practice to be aware of this order. You can re-order fields by dragging them.