When I searched out some block on Etherscan, I found out some strange thing.
For example, here is one of example: https://etherscan.io/block/9168614
Reward of this block is 2.18430490432165812 Ether (2 + 0.12180490432165812 + 0.0625)
2 ETH is mining reward and 0.12180490432165812 ETH is sum of tx fee.
Then what is 0.0625 ETH?
It seem that the value is not reward for uncles