Returns the numerator with formatting.

def str_numerator(self):
        """Returns the numerator with formatting."""
        unit_numerator, unit = UnitByte(self.numerator).auto_no_thousands
        if unit_numerator >= 10:
            formatter = '%d'
        else:
            formatter = '%0.1f'
        return '{0} {1}'.format(locale.format(formatter, unit_numerator, grouping=False), unit)