Windows Graphics Programming Win32 GDI and DirectDraw第六章疑問

標籤：width   art   io   cti   re   c   

《Windows Graphics Programming Win32 GDI and DirectDraw》6.1節中有這樣的描述：

The Windows NT/2000 graphics engine uses signed fixed-point numbers to represent coordinates, having a 4-bit fraction part and a 28-bit signed integer part. Points with negative coordinates or coordinates beyond the height or width of the device surface are considered clipped. So the maximum physical device size is 227 by 227, or 0.88 mile by 0.88 mile in 2400 dots-per-inch (dpi) resolution.

我自己算的方法是：2^27 / 2400 / 1000 = 559240.55 

作者給出的是0.88mile，感覺很疑惑。