Creating games with Limited Ranking for opponents, it doesn't work right!

Hi every one; I’m a little confused by the “Creating” games algorithms.
I Create several games to play with opponents Ranking from 13K to 9K, but I get players with 8K ranking or less, or some without any ranking at all, (?), accepting my challenges.
Why is that?
I appreciate any input on this please…
Thank you all.

13k is the default rank for a new account, and until you play certain number of games the rank shows up as ?

I wonder whether the site uses the individual category rank rather than the overall rank for this. For instance, someone might be 8k overall but 10k in 19x19 live. IMO, the site already uses individual category ranks to determine handicap and ranking, although I still haven’t received official confirmation on this: