I have a new-to-me Rollei 6008-I and wonder whether someone can identify what the 4th position on the meter dial on the left side of the camera does? The first three are Spot, Center Weight and Multi-Spot. Then at the very last (fourth) position is a Green shape. Maybe the shape was more clearly identified once upon a time, but I can't make it out at present. I cannot find a description of this in the manual. Maybe it's there, I just can't find it despite reading it over several times. Appreciate any help you folks can offer. Thanks!