Maybe they have some purpose, but it isn't immediately obvious. I tried Tree & List mode, they're never populated.

![image](https://user-images.githubusercontent.com/13134193/33488849-04a2c8a6-d6ed-11e7-85c3-5c05f1ec5346.png)

* Bitcoin-Qt 0.15.1 for Ubuntu 16.04 x64 (from http://ppa.launchpad.net/bitcoin/bitcoin/ubuntu xenial/main amd64)

Note: I just noticed I'm *not* seeing this on Ubuntu 17.10 x64 with 0.15.1 downloaded from bitcoincore.org. 

![image](https://user-images.githubusercontent.com/13134193/33491553-9584dc62-d6f5-11e7-9ba7-e074e0e36151.png)


l8->setText(BitcoinUnits::formatWithUnit(nDisplayUnit, nChange));        
    if (nPayFee > 0)
    {
        l3->setText(ASYMP_UTF8 + l3->text());
        l4->setText(ASYMP_UTF8 + l4->text());
        if (nChange > 0 && !CoinControlDialog::fSubtractFeeFromAmount)
            l8->setText(ASYMP_UTF8 + l8->text());
    }
    
    l7->setStyleSheet((fDust) ? "color:red;" : "");
    
    QString toolTipDust = tr("This label turns red if any recipient receives an amount smaller than the current dust threshold.");
    
    double dFeeVary = (nBytes != 0) ? (double)nPayFee / nBytes : 0;
    QString toolTip4 = tr("Can vary +/- %1 satoshi(s) per input.").arg(dFeeVary);
    l3->setToolTip(toolTip4);
    l4->setToolTip(toolTip4);
    l7->setToolTip(toolTipDust);
    l8->setToolTip(toolTip4);
    dialog->findChild<QLabel *>("labelCoinControlFeeText")      ->setToolTip(l3->toolTip());
    dialog->findChild<QLabel *>("labelCoinControlAfterFeeText") ->setToolTip(l4->toolTip());
    dialog->findChild<QLabel *>("labelCoinControlBytesText")    ->setToolTip(l5->toolTip());
    dialog->findChild<QLabel *>("labelCoinControlLowOutputText")->setToolTip(l7->toolTip());
    dialog->findChild<QLabel *>("labelCoinControlChangeText")   ->setToolTip(l8->toolTip());
    
    QLabel *label = dialog->findChild<QLabel *>("labelCoinControlInsuffFunds");
    if (label)
        label->setVisible(nChange < 0);
}
CCoinControl* CoinControlDialog::coinControl()