There are no ANDs. You matched on Char A/Char B. We opened an extra slot for extra requests that could have potentially been matched on instead, for example by someone offering Char A/Char C instead of Char A/Char B. You have to create a work based on one relationship (or "Char A & None") in your assignment. You could create something with Char A/Char B, or a different request they made for Char C & Char D, as long as it fulfills one of their relationship requests and does not violate one of their DNWs.

Does that help?