I’m of the personal opinion that these types of bullet points regarding curriculum should be covered by the GC and/or the school profile, not the student. It is the rare 17 year old that does not come across as whining when “explaining” such things.
The additional info section should not duplicate anything you already covered and should not be used as an overflow, eg expanding upon all your ECs because you could not fit the character count. It can be used to discuss any extenuating circumstances - family issues, financial issues, health (other than Covid) issues - that you think the college should take into consideration.
But it is also perfectly fine to leave blank.