I see targets marked as benchrest targets with a concentric circles like a traditional bullseye target, but they also have an empty square above the center of the bull similar to the example below. Would someone please explain to me the intended purpose this design? I know that anyone can use any target in any way, but I was wondering what the designers intended.

??? I am currently ignorant, not afraid of admitting it, but wish to end my ignorance on this particular matter. I suppose if I were a benchrest shooter, I'd already know the answer.

Thank you very much for sharing your knowledge.