Why it said “8-40 characters will be better” for the title field in the submission form?
Some directories have a limit in title length, some will require it be less than 30, some will require it be more than 10. So it’s better not to put a too long or too short title in the title field. Also most directories will not accept duplicate title names, so make sure your title is unique. Actually there are only around 10 directories have such limit, so SEO oriented and unique title is more important than the character limit.