0Josehf MurchisonBest Answer 4 years ago The number is the number of grains of grit per square inch. Look at it like teeth on a saw blade. 220 grit is 220 teeth per inch, it removes a lot of material and cuts fast but leaves deep scratches. 1,000 grit is 1,000 teeth per inch and it removes very little material takes forever to make a cut, and leaves a polished surface.So it works like this: 200 grit leaves deep scratches.400 grit removes the deep scratches and leaves shallow scratches.600 grit removes the shallow scratches and leaves fine scratches.800 grit removes the fine scratches and leaves very fine scratches. Last 1,000 removes the very fine scratches and leaves a polished surface.