Using a Bitcoin-Qt v0.16.0 ([downloaded from bitcoin page](https://bitcoin.org/bin/bitcoin-core-0.16.0/bitcoin-0.16.0-osx.dmg)) in an macOS High Sierra 10.13.4 

When I start after a fresh install Bitcoin-Qt as a mainnet node and wallet, the wallet prompt that about 203gb is going to be used in my disk
![image](https://user-images.githubusercontent.com/20187136/39899688-ba820bfe-5493-11e8-87d9-460ed5716a02.png)

When I start the node and wallet as testnet, shows the same message about the 203gb disk usage
![image](https://user-images.githubusercontent.com/20187136/39899756-17b31214-5494-11e8-8a57-60e604e74afb.png)

It seems that the second time the message is wrong, due that the testnet database uses about 14gb.
try {
        freeBytesAvailable = fs::space(parentDir).available;
        if(fs::exists(dataDir))
        {
            if(fs::is_directory(dataDir))
            {
                QString separator = "<code>" + QDir::toNativeSeparators("/") + tr("name") + "</code>";
                replyStatus = ST_OK;
                replyMessage = tr("Directory already exists. Add %1 if you intend to create a new directory here.").arg(separator);
            } else {
                replyStatus = ST_ERROR;
                replyMessage = tr("Path already exists, and is not a directory.");
            }
        }
    } catch (const fs::filesystem_error&)
    {
        
        replyStatus = ST_ERROR;
        replyMessage = tr("Cannot create data directory here.");
    }
    Q_EMIT reply(replyStatus, replyMessage, freeBytesAvailable);
}
Intro::Intro(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Intro),
    thread(0),
    signalled(false)
{
    ui->setupUi(this);
    ui->welcomeLabel->setText(ui->welcomeLabel->text().arg(tr(PACKAGE_NAME)));