Adler cites as a source the unedited Lexicon Ambrosianum.
The point of the entry would seem to be to illustrate a more rare way of saying "Greek" (as opposed to the common Ἑλληνικός ). The phrase in the gloss -- or more exactly the secondary headword phrase -- appends the same form of the adjective to a feminine noun, and thus shows that the adjective is of the two-termination variety.