They are just regular characters ÿ Ø ÿ Û using CP1252 encoding¹ (basically Windows’ proprietary legacy ANSI² encoding for the western world). You can also leave them off (like in my additional symbols), they are just skipped, as far as I can tell. I guess they are intended as marker but unfortunately they mark a file as a corrupted JPEG outside of QSPICE (like if you want to upload the file as *.txt in this forum³).
¹ The blue text are links and readers are supposed to click them.
² I don’t know how well it works with Japanese Windows where ANSI is a variant of Shift JIS.
³ This rejection and more could probably be configured but it looks like they are still getting familiar with the forum software.