Lol, I quit at level 6. The highest level I saw was Kokushi, level 20 the last time I saw him a few days ago. In that time, he probably leveled quite a bit. I saw a lot of late 1x's, too. O.O Congrats on 10, Chesters!
EDIT: OH, GEEZ! THE EXP REQUIREMENT GETS EXTREMELY HIGH!!! How did Kokushi...? >.>