From this article link
ALTER TABLE table_name AUTO_INCREMENT = value;
You specify the table name after the ALTER TABLE clause and the value
which we want to reset to in the expression AUTO_INCREMENT = value.
Notice that the value must be greater than or equal to the current
maximum value of the auto-increment column.
But actually i can create User by assign ":id" property equal smaller then 10000.
User.create(:id=>1, :name=>'William')
Thanks @SRDP too.
IMPROTANT:
You user id may start from 1 if you set :id = 1 first. So set a user from 10000 first, then create any user below 10000.