When should the proccessing of the SPF record end?

In spf-draft-20040209.txt in the section 3.2 it says:

   Each directive is considered in turn from left to right.

   ...

   If it matches, processing ends and the prefix value is returned as
   the result of that record.  (The default prefix value is "+".)

But then in section 5.2 the example is:

   v=spf1 mx -all exp=explain._spf.%{d}

This means that the 'exp' directive is never processed because according to
3.2 the processing ends at '-all'.

Roger