In fact, I did not know what is the petitioner letter or cover letter.
When I collected all of my letters, I just thought I should have wriiten so-called summary or something as an intro. I did it, sent it, and got approved.
Till now, I don't know that 5 pages should belong to petition letter or cover letter.
When I wrote that 5 pages, I did use the letters' words just trying to intro my academic stull.
Thanks for asking.