I have a wall with a water table at 3'-0" that has a 1 1/2" reveal. I insert my windows, but the sill is offset by 3/4" for some reason. I'm sure it has something to do with the water table, but I can't figure it out. If I try to move the window, just the window moves, not the sill. I've tried different display settings, but nothing works. Any ideas? I've attached the drawing.