If the sticker has…
–four digits, it is a conventionally grown product, meaning that it is grown with all the pesticides and fertilizers that organic produce lack
–five digits and begins with an eight, it is a genetically modified food
–five digits and begins with a nine, it is organic
I think this is especially useful for the genetically modified food groups, since grocers don’t put up signs for that the way they do for organic produce. You will also be able to tell if some produce is mislabeled as organic. Be aware that there are some grocers who don’t follow these guidelines – but it’s a good rule of thumb!