Transaction Fees – How does fee subtraction work in Bitcoin Core?

In the explanation of Bitcoin Core, subtractfeefrom A parameter that defines which recipient address will be selected to receive a smaller amount and contribute to the fee payment.

Use cases include:

Alex has 1 utxo with 10btc and sent TXN of 1BTC each to Mary BTC and BOB. The fee is 0.5BTC, so the change amount to Alex would be 10-2-0.5 = 7.5BTC.

How to? subtractfeefrom Would you like to apply it in detail to the above case?

My high level assumption is

• Get the fees you need for txn
• Deduct this amount equally for all optin output destinations except change output (e.g. 0.5BTC/2 destination)
• The first optin output object is also deducted as an indivisible amount. Example: 0.5BTC % 2 target
• Check if the deducted output is dust, otherwise continue.
• Add total deduction for change of address

Additionally, if there is no change output, should I generate output in this case?