Thank you! Your explanation was very easy to understand.
If 30% withholding tax is included, the amount of available balance is quite close.
I'm sorry to bother you, but could you let me ask one more question?
My country has a tax treaty with the US, so I'm not subject to the 30% withholding tax. I have submitted the W8BEN-I to itchio as proof.

Therefore the estimated balance should be:
12 - (0.5 + 12*3% PAYMENT FEE) - 12*0% WITHHOLDING TAX - 12*0% ITCH REVENUE = 11.14 per sale * 7 sales = 77.98 approximate
The available balance is listed as $54.81, can I withdraw $77.98?