That’s the trophy gotten for all weapons in the DLC. Only the last one for the optional boss fight, that I might have missed the first time around.
I took my NG++ character into the DLC and lost about 400,000 blood echoes, so I can confirm that the DLC scales like a bastard with NG+. My recommendation for @Sly Reflex is to keep a save of before the final boss and then use that character to go through the DLC.
I’m at the point now where my second character has not completed the main game but has access to every weapon and every lamp location so can help out with anyone that fancies a bash through.