Why are withholdings higher for some tournaments I've won?

Withholdings may be higher for a particular tournament because all or part of the entry fee was paid using Game Credits (Promotional Credits, Entry Fee credits, etc.). Entry fees that are paid using Game Credits cannot be subtracted, so the Net Winnings and the amount withheld will be higher.

Net Winnings are calculated as your winnings minus the entry fee for the tournament that was won. Game Credits are generally awarded from a promotional bonus or entry fee refund that you had received from WorldWinner®.