It's been a long time since I've played, and I'm starting the 2nd DLC now. Can anyone refresh my memory on what the three symbols on the signs above the doors mean? I just finished one section and two of the symbols are dark (I collected two items and got the points for them), but I can't see where a third item would be in that section. Am I just missing a third item and that's what the third symbol on the sign means?

EDIT;: Nevermind, I figured it out. I was missing one of the items. I collected it and now all three symbols are dark.