I'm reading *Emacs Lisp Intro* by Robert J. Chassell.

In 6.1 The ‘`save-restriction`’ Special Form
> when you use both ‘save-excursion’ and
‘save-restriction’, one right after the other, you should use
‘save-excursion’ outermost.  If you write them in reverse order, you may
fail to record narrowing in the buffer to which Emacs switches after
calling ‘save-excursion’.

And in 6.2 `what-line`
> (Note that the ‘(widen)’ expression comes between the
‘save-restriction’ and ‘save-excursion’ special forms.  When you write
the two ‘save- ...’ expressions in sequence, write ‘save-excursion’
outermost.)

I'm really confused about why it should be written like this:
```lisp
(save-excursion
  (save-restriction
    BODY...))
```

Any help is appreciated!