[Softwires] MAP-E question -- first prefix

[Tom Taylor <[e-mail]>]

In Section 5.2 of -map-05, there is the paragraph:

The MAP subnet ID is defined to be the first subnet (all bits set to
    zero).  Unless configured differently, a MAP node MUST reserve the
    first IPv6 prefix in an End-user IPv6 prefix for the purpose of MAP.

Question: does the second sentence say anything different from the first 
one?

Question: if the MAP node is configured differently, how will other 
nodes be able to synthesize its MAP IPv6 address from the FMR?

Tom Taylor