There's one mail thread, which I can't `set seen' so this folder's box can't
reduce the counter because of that. I think, if I restart meli and go straight
to this folder and set seen for these emails, then it will get read, but not
doing it right away, it gets stuck, even going inside thread and trying read
each email, it doesn't work.
When this happens, after I execute `set seen', meli gets two colored lines at
the bottom of screen, orange and red, and it's stuck there for quite long time
then it simply goes away.
I've noticed that sometimes when that happens, if I have meli closed much later,
when opening it again, the emails have been already `set seen' and the folder counter is zeroed.
So it seems that
meli was in some broken state formerly where it didn't update to the real state
of the mails / folder.