0xac9650d8?0xac9650d8 is the function selector for multicall(bytes[]). Runs several calls in one transaction.
When a transaction's data begins with 0xac9650d8, it is calling multicall. The selector is the first four bytes of the keccak-256 hash of the signature multicall(bytes[]), which is how wallets and explorers work out which function a payload is for.