It is important to remember that the Nutrition Facts label lists the items that are required by law to be listed on food products. Potassium, Ca, Mg etc may be listed as percent daily values, but since they are not required to include exact amounts, they do not and neither do the data base. This will make your reports inaccurate unless you are entering the nutrient amounts yourself using a more comprehensive tool to obtain you numbers.
Following a DASH eating approach is a great way to help limit sodium intake while promoting foods high in potassium and magnesium. Here is a helpful outline to get you started.
High Blood Pressure? Have a DASH of Spark
There's More to it than Your Sodium Intake www.sparkpeople.com/resource/nutrition_art