That would be 13 cups (unit of measure) of cereal a day, probably 4-6 bowls depending on how generous you are when pouring it into a bowl. Or 13 slices of bread (which is most of a loaf). That doesn't seem at all like a reasonably recommended number. Trying to find real charts, it looks like by 1992 they were recommending a range of 6-11 servings of grains (rice, cereals, pasta, breads). Which is at least a more reasonable number if you swing towards the low end.