Mistake in section 4.4 of User's Guide?

Hello,

This is regarding section 4.4, Page Numbers and Running Headers. According
to this section, the proper way to have a header/footer that says Page X of
Y is by { Page @PageNum of @NumberOf last.page }.

However, I could not get this to work. I'd get an Unresolved reference to
NumberMarker. However, I found this command to be successful: { Page
@PageNum of @PageOf last.page }.

Did I screw something up that makes @NumberOf not work or is perhaps the
User Guide showing a deprecated method of accomplishing this?

Using Lout 3.38.

Michael