Did you request a withdrawal and receive that amount?
Along with the money, you should have access to a file with the details of each transaction, showing the exact charges for each sale you made.
If you haven't requested a withdrawal yet, there are three things you should keep in mind: first, the amount shown is only an estimate, not the actual amount you'll ultimately receive.
Second, the withholding percentage will be corrected when your interview is validated, and that happens when you request a withdrawal. If you haven't requested one yet, it's normal to see a provisional 30%.
Third, in addition to the withholding, when the sale price is low, the biggest loss you'll incur is from payment processor fees, which, in addition to a percentage, have a base value of about $0.70 USD per transaction.
P.S.: I forgot, the first time you request a withdrawal, you'll incur a $3 fee to validate the interview.