Regarding the pictures you posted....The first set is the scale for Specific Gravity... SG. It is the one almost everyone refers to when talking beer. The second set is basically useless for beer and is used more for wine or mead, where the potential to reach a final reading of 1.000 or lower. It is "potential" alchohol. We never use that one for beer. The 3rd set of pictures is for a scale called Brix or Plato. You will learn about that one later, ignore it for now.