Sortcode limit to one Category

I’m trying to use the Recent Posts Widget Extended shortcode, not the widget, in a page we are using for an internal blog. Since its internal, I only want the category “internal” to show with thumbnails. Try as I may, I just don’t seem to be able to get it to filter to only the internal posts:

Here is my shortcode.

[rpwe limit=”10″ orderby=”date” thumb=”true” post_type=”post” category=”1287″ excerpt=”true” readmore=”true” readmore_text=” Read More >>”]