I have 2 doubts regarding setting permissions:

Query no.1:

[root@station1~]#ls -ld /testdir
drwx------ 2 sam sales 4096 May 22 14:08 /testdir

[root@station1~]#chmod u=rwx,g=r-x,o=r-x /testdir
[root@station1~]#ls -ld /testdir
drwxr--r-- sam sales 4096 May 22 14:08 /testdir

Please let me know why it is happening...

it should be drwxr-xr-x, is it not?...
but if I do it in the numeric way it is working fine...also if i do like the following it works fine:

chmod u+rwx,g+rx,o+rx /testdir.

QUERY no.2

When I create a file in CLI mode its default permissions are 644, but when I create a file with gedit in GUI mode it is 600. Why is it this way???

Thank you.

No, the dash means write (w) permissions are not set, so you have added read permissions and removed execute (x)

try chmod u=wrx,g=rx,o=rx /tesdir

thanks a lot. Please have a look at my 2nd query too...