QPrinterInfo::supportedResolutions() return wrong values

#include "mainwindow.h"
#include <QApplication>
#include <QPrinter>
#include <QPrinterInfo>
#include <QDebug>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);    
    QList<QPrinterInfo> printers = QPrinterInfo::availablePrinters();
    for(int i = 0; i < printers.size(); i++)
    {
        QList<int> infoDpi = printers.at(i).supportedResolutions();
        for(int j = 0; j < infoDpi.count(); j++){
            qDebug() << printers.at(i).printerName() << " " << infoDpi.at(j);
        }
    }
    return a.exec();
}