Fix typo in contract reference number (ethereum#4491)

EIPS/eip-2309.md

@@ -102,11 +102,11 @@ Events in Solidity can have up to three indexed parameters which will make it po
 
 This can lead to bugs and unnecessary complex logic for platforms using these events to track token ownership. When transferring a single token it is acceptable to emit the original `Transfer` event, but the `ConsecutiveTransfer` event should not be emitted during the same transaction and vice-versa.
 
-**Comparing 2039 and 1155**
+**Comparing 2309 and 1155**
 
 As the NFT market continues to grow so does the need for the ability to scale the smart contracts. Users need to be able to do things like mint a massive amount of tokens at one time, transfer a massive amount of tokens, and be able to track ownership of all these assets. We need to do this in a way that is cost effective and doesn’t fail under the confines of the Ethereum blockchain. As millions of tokens are minted we need contracts with the ability to scale.
 
-[ERC-1155](./eip-1155.md) was created and added as a standard in 2019 to try to solve these problems, but it falls short when it comes to minting massive amounts of unique tokens in a cost-effective way. With ERC-1155 it’s either going to cost hundreds (or thousands) of dollars or it’s going to run out of gas. ERC-1155 works well when minting many semi-fungible tokens but falls short when minting many unique tokens. Using the 2039 standard you could mint millions of blank NFTs upfront and update the metadata for each one in a cost effective way.
+[ERC-1155](./eip-1155.md) was created and added as a standard in 2019 to try to solve these problems, but it falls short when it comes to minting massive amounts of unique tokens in a cost-effective way. With ERC-1155 it’s either going to cost hundreds (or thousands) of dollars or it’s going to run out of gas. ERC-1155 works well when minting many semi-fungible tokens but falls short when minting many unique tokens. Using the 2309 standard you could mint millions of blank NFTs upfront and update the metadata for each one in a cost effective way.
 
 
 ## Backwards Compatibility