I don't get it.

I mean, I get the words at the bottom, and that the implication is that Dr. Pepper, like Captain America, is one of a kind.

But I don't understand what the image, slash and number are meant to communicate, exactly. Is it...a fraction gag, of some kind...? Or math...? That Captain America can't be reduced further than Captain America...?

I don't know. But now I associate Captain America and Dr. Pepper with forgotten grade school math and overall confusion, and therefore would prefer to avoid them both. It's Batman and Mr. Pibb for me.