0x55f804b3?0x55f804b3 is the function selector for setBaseURI(string). Changes where the collection metadata is served from.
When a transaction's data begins with 0x55f804b3, it is calling setBaseURI. The selector is the first four bytes of the keccak-256 hash of the signature setBaseURI(string), which is how wallets and explorers work out which function a payload is for.