File dispostion problem

I’m developing a Windows 2000 filter driver. I’m trapping the IRP_MJ_CREATE
IRPs. While doing so, I’ve observed that for File creation (FILE_CREATE) the
disposition value is 0x00000005 whereas for Overwrite_if(FILE_OVERWRITE_IF)
it is 0x00000002. But in the windows 2000 ddk - ntddk.h it is defined as :

#define FILE_SUPERCEDE 0x00000000
#define FILE_OPEN 0x00000001
#define FILE_CREATE 0x00000002
#define FILE_OPEN_IF 0x00000003
#define FILE_OVERWRITE 0x00000004
#define FILE_OVERWRITE_IF 0x00000005
#define FILE_MAXIMUM_DISPOSTION 0x00000005

Is it a bug in the header file? Please confirm.

Thanks in advance for the help.

Arun.