What does the %12.10lg means in C++ strings formatting

I have seen this piece of code in one of the C++ project in windows environment. just wondering what does the meaning of %12.10lg. Anyone has idea?

class Point 
{
 double x, y;
 public Point::Point(double x_cord, double y_cord)
 {
  x = x_cord;
  y = y_cord;
 }
}

void foo(){
  Point ptStart(12.5, 33.5678)
  TRACE("%12.10lg, %12.10lg, %12.10lg\n", ptStart)
}