Salt - Salt/Sand - Sand spreaders, what does it mean?

Some fun mixing limestone screenings with an ice melt product and a quick study of spreader labeling. As tempting as it was to just use a cheaper tub of sand instead of ice melt, my SHPE1000 spreader is label as salt/sand 50/50 spreader. Dumping jut sand in teh hopper wouldn't have turned out well, or for any product just labeled "Salt Spreader".... or "50/50". I mention in the video a couple of times about this mix because of my auger type, but it isn't just because it is an auger feeder. Poor material feeds can occur in ANY spreader without vibrators, agitators and a combination of proper shape and material.