0x5ae401dc?0x5ae401dc is the function selector for multicall(uint256,bytes[]). Runs several calls with a deadline.
When a transaction's data begins with 0x5ae401dc, it is calling multicall. The selector is the first four bytes of the keccak-256 hash of the signature multicall(uint256,bytes[]), which is how wallets and explorers work out which function a payload is for.