The Ra Material and Urantia

[Infinite]

Is The Urantia Book not real or did Ra mean something else by this?

Well, Ra meant that was passed by entities that inhabited the inner planes of the Earth. Personally, I found some distortions in the Urantia Book, such as the statement that astrology is just superstition. Another problem is the naming of many beings and places that we have no way of knowing if they are real. They also talk about Lucifer as an archangel. Ra implies that Lucifer is a Logos.

Also, what are the inner planes?

It is the time / space portion of the Earth. The invisible / metaphysical dimensions of our planet, such as the astral plane, the mental plane, etc.