wrong section to create thread.

[geevest.com]

hello i have a problem.
if i create a thread in category D , it show in category A,not in category D
but if im move thread < B > in category A its work.
i dont know why,

ex : if i click category D its direct to category A

-1st ROOM
--ABC room
---category A
---category B
---category C

--DEF room
---category D
---category E
---category F