Existing:

When an element is bound to an extensible value set, derived profiles may state rules on which codes can be used, but cannot define new or additional codes for these elements unless no codes with appropriate meanings are found in the base value set.

Change to below because it is the binding that is extensible, not the value set per se.

When an element is bound *using extensible strength to a *value set, derived profiles may state rules on which codes can be used, but cannot define new or additional codes for these elements unless no codes with appropriate meanings are found in the base value set.