data to the presentation serveru0093default value for user dialog??

Q] Please see this link

http://help.sap.com/saphelp_46c/helpdata/en/fc/eb3d83358411d1829f0000e829fbfe/content.htm

FILENAME = 'd:\temp\saptest.xls' this is what we are exporting but it has been said to be

FILENAME Filename (default value for user dialog)

Then what does “ default value for user dialog” means exactly?