I was reading this very interesting page: https://slushpool.com/help/hashrate-proof/
I read the "How does the mining and hash rate calculation work?" section and with a fixed difficulty for all miners it all made perfect sense. But the there is this phrase:
The value of 2^32 was chosen arbitrarily in the past, but is stable and makes one share well defined. In reality, proof of work value may vary from miner to miner, but it is just an implementation detail.
Except that I cannot figure out exactly that "implementation detail". How do you factor variable difficulty of each miner in how you count shares exactly? What would be the exact formula to compute the % of rewards for each miner?