Tizen Developers

I'm reading the edc codes for button.edc. The code is at line 34 of below file :

https://review.tizen.org/git/?p=framework/uifw/efl-theme-tizen.git;a=blob;f=2.3-mobile/widgets/button.edc;h=e6587731db87acb7397724f3407110b399489a70;hb=refs/heads/tizen_2.3.1

The images define as:

images {
    set {
        name: "core_list_button_bg.#";
  image {
      image: SMALL"images/Controls/core_list_button_bg.#.png" COMP;
  }
  image {
      image: MEDIUM"images/Controls/core_list_button_bg.#.png" COMP;
     }
 }
}

I searched the edc documentation, the format for image definition is:

    image   [image file] [compression method] 

And the samples are:

images {
    ..
    set {
        ..
        image {
           image: "filename4.ext" COMP;
           size: 51 51 200 200;
           border: 0 0 0 0;
           border_scale_by: 0.0;
        }
        ..
    }
}

So I'm confused where is the definition for SMALL and MEDIUM, and what is the definition for image section in Tizen EDC version.