I've been learning about mining as part of a pool and using the Stratum protocol to submit completed work back to a pool -- https://en.bitcoin.it/wiki/Stratum_mining_protocol . There is this parameter, "ExtraNonce2," a value that the miner keeps changing. Could someone tell me a scenario where a pool worker submits a nonce that correctly hashes the data it was given according to the difficulty, but it submits an "ExtraNonce2" value that causes the mining pool to reject the submission?