Simple answer is the calc is giving you the long term view, you wont see an exact match in returns for short periods and also it can depend on the pool used and their size relative to the network.
Here is a list of coin stats:
https://www.coinwarz.com/cryptocurrency/?sort=blocktime&dir=asc
HI STT,
thanks for you reply, but still not clear
I.e. if you will take cloud mining like https://www.genesis-mining.com/pricing - how to understand how many ETH you will get form 100 MH/s for 1 month?
I'd like to program this function to compare profitability, but I don't understand formula(( and can't find it