The arrow is pointing out the first of seven word types. This column was once occupied by suffixes. I hope you appreciate this revision as an Improvement, as I do. The main benefit is that one could change a word category (verbs into nouns, et cetera) or specify parts of speech category.
(1) verb (arrow)
(2) adverb
(3) noun
(4) pronoun
(5) adjective
(6) preposition
(7) conjunction
Interjections shall be listed under the LANGUAGE lexicon