XPath question

This might not be the right forum, but seeing as XSL references XPath I
think maybe people here can help me!

I cannot understand why the following statement is true in the XPath spec:

"NOTE: The meaning of a Predicate depends crucially on which axis applies.
For example, preceding::foo[1] returns the first foo element in reverse
document order, because the axis that applies to the [1] predicate is the
preceding axis; by contrast, (preceding::foo)[1] returns the first foo
element in document order, because the axis that applies to the [1]
predicate is the child axis."

(taken from http://www.w3.org/TR/xpath#node-sets)

I just couldn't derive this from my reading of the spec, despite trying
multiple times. If some wiser person could kindly guide me through the
reasoning of why this is so I'd really appreciate it.

Toby Ferguson
ELOAN


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