That is a function called bidAndWithdraw. When the rebalance of a Set portfolio is initiated on the Set Protocol, this is one of the functions which will be executed on the Ethereum blockchain. A blockchain transaction is basically the footprints left by the smart contract after its execution. In that transaction, you can find the name field of the function is bidAndWithdraw. The params fields are _rebalancingSetToken, _quantity, and _allowPartialFill .