Start from what a changeover actually costs you. The calculator returns a fee that covers it, the amount you absorb every month if you charge less, and the all-in nightly price a guest ends up comparing.
There is no correct number, and anyone quoting one has invented it. A cleaning fee is a cost recovery, so it starts at what the changeover costs you: the cleaner's invoice, laundry, consumables, and your own time if you do it yourself. From there you have three honest choices, and each one moves money between the fee and the nightly rate rather than creating any.
If the fee is pushing one-night guests away, the fix is often the stay rule rather than the fee — see minimum stay settings and orphan gaps. If you are trying to hit a monthly number rather than cover a cost, start from the other end with the nightly rate calculator.