What does this mean?

I found this on Page 34 of IEEE EDITORIAL STYLE MANUAL, it's about how to edit the reference. I don't understand the following sentence:

NOTE: The only exception to this rule is PROCEEDINGS OF THE IEEE, which never carried an acronym on the masthead

Does it mean when cite a paper from PROCEEDINGS OF THE IEEE, do not cite it in an abbreviation form. If it is, why the following example ( Page 35 of IEEE EDITORIAL STYLE MANUAL) gave an abbreviation form: