referrer is 0x0000000000000000000000000000000000000000 in this case. You will get 100 USDT or USDC (depending on the active token) for successfully executing this.
~80% of all collected fees are used to buy back GLO from the active token's pool and that, paired with the remaining ~20%, is optimistically re-added to the pool.
By default, the active token is toggled between the USDT and USDC with each execution. However, the active token will remain the same across executions if insufficient fees have been generated in the token that should've been next.