I found out that I have to use ALL the crystals - no leftovers allowed. As I have already matted and mounted the piece on a backing, and the two large red crystals just do not fit into the design, I took their suggestion of using the extra crystals as part of a "signature".
The addendum piece is a separate piece:
To be associated with the main piece however they feel appropriate:
I've decided to mail the whole thing in, as it is a small piece, and the crystals are difficult to photograph with their reflections. Even though it's not due till mid-January, they say I can mail it in now.