0x437823ec?0x437823ec is the function selector for excludeFromFee(address). Exempts an address from fees.
When a transaction's data begins with 0x437823ec, it is calling excludeFromFee. The selector is the first four bytes of the keccak-256 hash of the signature excludeFromFee(address), which is how wallets and explorers work out which function a payload is for.