You forget that there is a lot of water too. As high as a food is in minerals, these minerals will always be found in relatively small amounts.
On http://www.nal.usda.gov/fnic/foodcomp/search/ you can see the breakdown of many food (blackstrap molasses is not listed although regular molasses is). Usually, "ash" represent the total amount of minerals. Don't forget that this will by example include the "carbonate" part in calcium carbonate.