[Vorbis] Block sizes

[Tony O'Bryan]

For the Vorbis file I'm using to develop my decoder, I've read the Ogg header 
at the start of the file, and now I'm reading the Vorbis identification 
header.

Everything checks out fine until I get to the block size byte (offset 28 
starting at the packet type field).  The byte value here is 184, which is a 
bit pattern of: 1011 1000.

The low order 4 bits are 8.  Squaring it gives 64.  This is valid according to 
the specs (as I understand them).  The upper 4 bits are 11.  Squaring it 
gives 121.  This is not valid according the the specs:

"Allowed final blocksize values are 64, 128, 256, 512, 1024, 2048, 4096 and 
8192 in Vorbis I."

Does that requirement only apply to block_0?