Starting on page 6, there is a section labeled "Special Entries" which has the following introduction:
"Certain creatures, such as devas, have special abilities or live in unusual places, etc., and these may require the notations explained below."What follows are explanations for monster stats such as "Plane", "Intelligence as it affects spells", "Constitution", and several others, which look like they were originally intended to be listed in at least some monster listings as standard stats, but it appears as if the idea was dropped and the excision never made to the "How to Use this Book" section at the front. Only the stat on "psionic ability" seems to have been used at all. Even the entry on devas doesn't have a listing for "Plane".
I know things were a bit hectic in 1982/1983 at TSR, but this is an entire page of material that seems to have been included as an oversight. Yikes!