Please could you confirm you are using the old Frostwire 4.21.8 or earlier.
If you are, The trash can indicators are somewhat randomly created and are not connected with your download history. They show what Frostwire "thinks" are junk and become more useful as you unmark non junk items and mark junk items, and in this way Frostwire "learns" what is most likely junk. Many Junk files Gnutella files are identical except for the name which can be automatically generated to match your search term.
I am not sure why your appdata folder shows at that size. It should not. Did it contain ANYTHING?
Please see Also THIS POST
will be very useful, for using Frostwire 4
I hope this helps a bit.