It's been said thousands of times on the forum.
The value shown is an estimate; the actual, detailed value is only generated at the time you request payment, not before.
The formula per sale would be:
Receive = Price - Payment Processing Fees - Itch (10%) - Tax Withholding, if applicable (30% default).
The Payment Processing Fee is a fixed amount + a percentage of the price. Due to the fixed amount (approximately $0.50), for small transactions, $1 or $2, it's usually what causes you to lose the most profit.
Tax Withholding is the biggest cause of error between the initial estimated value and the final value you receive, as it depends on your country and the buyer's country, so there's no easy way to estimate its value.
You should see the current value in your tax information settings.
https://itch.io/user/settings/seller/tax-information
If you need to make changes to your interview, you must contact support so they can generate a new link to complete the interview.
However, the interview costs $3 and is therefore only validated when you request a payment. This means you can complete the interview and not see any changes to your withholding percentage unless you request a payment.