From oggdropXPd_-_User_Guide.html :

"Ogg vorbis does not offer true CBR encoding, an emulation is provided that comes very close. This method should be used where the strictest control over encoding bitrates is required. In CBR mode, Min. Bitrate, Nom. Bitrate and Max. Bitrate boxes are used to define floor, mean and ceiling bitrates."

I think it should be:

"...In ABR mode, Min. Bitrate, Nom. Bitrate and Max. Bitrate boxes are used to define floor, mean and ceiling bitrates."

In CBR mode you can't use the Min. Bitrate and Max. Bitrate boxes 'cause they're locked.

Thanks for OggdropXPd .

BTW I've just checked the latest User Guide (3rd draft) from your page.

You're right, of course!! Thanks. Fourth Draft uploaded.