Any old hand knows that an anchored boat looks tighter in to the rocks from her deck than she ever does from the shore. A useful reassurance if you have radar is to set the electronic range ring to touch the nearest bricks and see how close they really are. In this case, the skipper has set the ring to the same diameter as the scope of cable he has laid. As a further refinement, he has estimated the probable position of his anchor and placed the cursor on it to delineate his swinging room requirement.
The electronic chart reproduction of the same situation backs up the radar image by delivering data from an independent source. A sound plan, because the rocks just might be a poor radar target.