This is straight out of Reader's Digest:

Those little stickers on fruits and vegetables at the supermarket
aren't just for the checkout clerk to find the price. You can use
the numbers to figure out how the produce you're buying has been
grown.

A sticker with four digits means the food was conventionally grown.
Five digits starting with an 8 indicate genetically engineered
produce (the food's genetic material has been altered), and five
digits starting with a 9 means the food was organically grown
(without the use of most conventional pesticides or synthetic
fertilizers).

Don't worry if you can't remove all the sticker adhesive - it's
required to be safe to eat.

(writer: Neena Samuel)