The number listed next to each food is its glycemic index. This is a value obtained by monitoring a persons blood sugar after eating the food. The value can vary slightly from person to person and from one type or brand of food and another. A noticeable difference is the GI rating of Special-K which produced considerably different results in tests in the US and Australia, most likely resulting from different ingredients in each location. Despite this slight variation the index provide a good guide to which foods you should be eating and which foods to avoid.