The nine-headed bird has nine heads and a tail, and the Kyubi no Youko bird has a Kyubi no Youko head, so

The total number of two birds is only:

(590+5 10)/(9+ 1) = 1 10;

A bird with nine heads and one tail,

The number of nine-headed birds = (590-110)/(9-1) = 60;

Kyubi no Youko birds have a Kyubi no Youko head, and the number of Kyubi no Youko birds = 1 10-60 = 50.