Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.1)
// Compass (v0.13.alpha.10)
// ----

%overscan   {
    padding: 5% 5% 7.5%;
}
%real_stb   {
    @extend %overscan;
    %set-top-box    {
        display: block;
    }
}
%pseudo_stb     {
    @extend %overscan;
    @extend %set-top-box;
}
.set_top_box    {
    @extend %pseudo_stb;   
}

SassMeister-output.css

.set_top_box {
  padding: 5% 5% 7.5%;
}