According to a report of bug id 1676,

Althogh commands below are written in smb.conf, "%G" never changes into a group 
name.
  security = ADS 
  template homedir = /home/%G/%U 
  template shaell = /bin/bash
  winbind use default domain = yes

For exemple:
With this directive, when using "getent", we should get:  
$ getent passwd  
....  
miracle2:x:10006:40003:miracle2:/home/dev/miracle2:/bin/bash
....  
  
Here is what I actually get:  
miracle2:x:10006:40003:miracle2:/home/40003/miracle2:/bin/bash


With investigating file "source/lib/substitute.c", I founded that the return 
value of "gidtoname" function is not a group name, but is still gid.