I don't think anything you can change in SE11 will influence that tag - it's generated by SAP along with the web service.
If it is possible at all you may be able to change the interface in the actual web-service. (However it's likely that if you have to regenerate the web-service your changes will be overwritten again).
Sorry I don't have access to a system where I can check this at the moment.
If you can post some screenshots of the web service interface in SE80 someone else may be able to help.