They actually have significance in telling you more about your purchase.
Assigned by the International Federation for Produce Standards (IFPS), the four to five digit number serves two major purposes.
The first is to allow the cashier to look up the allocated price while the second plays a more pivotal role as it helps determine what the produce is and how it was grown.
This works by following the first number. If it's a 0 it indicates the food was conventionally grown, while a 9 identifies organic produce.
If the sticker is missing from a fruit or vegetable (it's not mandatory for all supermarkets and growers) you can instead look for worded stickers labeling if they are organic or not.