.. so the WHERE clause mathes that number of rows. To comment further will will need the CREATE statements for the tables as well as the (JOIN-)query you are referrring to.
BTW: Instead of verbose explain it is most often better to paste the SQL – it is non-ambigious and can even be imported/executed at our end.
Okay, thanks a lot, Peter – both for the answer and the tip. Next time I'll also check the FAQs before I post a question. (This was my first post and I only checked the Forum.)