C#做一个类似流量监控的软件，绘制波形图的时候用到了这个函数，请问其中我标注问好的是什么意思？

private void PaintMe()
        {
            int num5;
            int width = base.ClientRectangle.Width;
            int height = base.ClientRectangle.Height;
            if ((width == 0) || (height == 0))
            {
                width = 1;
                height = 1;
            }
            this.pictureBox1.Width = width;
            this.pictureBox1.Height = height;
            Bitmap image = new Bitmap(width, height);
            Graphics graphics = Graphics.FromImage(image);//???
            //绘制背景表格
            int num3 = width / this.m_GridSize.Width;
            int num4 = height / this.m_GridSize.Height;
            Pen pen = new Pen(this.m_GridColor);
            for (int i = 0; i <= num3; i++)
            {
                num5 = width - (((i * this.m_GridSize.Width) + this.m_GridStartPos) - 1);//??
                graphics.DrawLine(pen, num5, 0, num5, height);//??
            }
            for (int j = 0; j <= num4; j++)
            {
                num5 = (j * this.m_GridSize.Height) - 1; //???
                graphics.DrawLine(pen, 0, num5, width, num5);  //????
            }
            //绘画线条
            int num8 = width - this.m_GridMoveStep;
            int num9 = this.aList.Count - 2;
            Pen pen2 = new Pen(this.m_LineColor);
            while (num9 >= 0)
                {
                    float num10 = ((float) this.aList[num9]) / this.MaxValue;
                    float num11 = ((float) this.aList[num9 + 1]) / this.MaxValue;
                    int num12 = height - ((int) (height * num10));
                    int num13 = height - ((int) (height * num11));
                    graphics.DrawLine(pen2, num8, num12, num8 + this.m_GridMoveStep, num13);
                    if (num8 < 0)
                    {
                        break;
                    }
                    num8 -= this.m_GridMoveStep;
                    num9--;
                }
          流量监控，高仿管理器流量Bitmap软件