When using attribute_view_gui, you're calling up the template for the datatype that is used to represent some data within the content object that you're accessing. In this case, the system is probably accessing the view template for the ezbinaryfile datatype. This template is located here:
You should make your own ezbinaryfile.tpl and place it inside your design (simply copy the one from the standard design and remove the printout of the size);
