Wow, my braille is rusty.

The rectangle that is empty is to indicate the colour (in this case, red if I am not mistaken). The solid rectangle is white. So someone can feel it and tell what the colours should be (it is essentially a legend for a tactile diagram). I think it says 13 white and 13 red stripes.

The last line says fifty white stars on blue field, and then shows what a star feels like.

I can read braille but not familiar with these. Can you snap a pic?

In contracted English Braille, a full cell (⠿) stands for the word "for". The symbol is also often used as a placeholder. Not sure what you mean by open and closed rectangles...

interesting never saw something like that. Sounds interesting though.