https://github.com/bitcoin/bitcoin/blob/5180a86c96bc05d2a731f70f36aae28ab5a3fad4/src/qt/sendcoinsdialog.cpp#L339

I think this is %1, not %2
{
    updateYesButton();
    countDownTimer.start(1000);
    return QMessageBox::exec();
}
void SendConfirmationDialog::countDown()
{
    secDelay--;
    updateYesButton();
    if(secDelay <= 0)
    {
        countDownTimer.stop();
    }
}
void SendConfirmationDialog::updateYesButton()
{
    if(secDelay > 0)
    {
        yesButton->setEnabled(false);
        yesButton->setText(tr("Yes") + " (" + QString::number(secDelay) + ")");
    }
    else
    {
        yesButton->setEnabled(true);
        yesButton->setText(tr("Yes"));
    }
}