SIP Extension Wrong password Error

Hay,
I am using freepbx.i want to add a sip extension with 4 digit self secret.i have edited the sip_general_custom.conf file and but in log files i get wrong password error.belowis my config

[7500]
deny=0.0.0.0/0.0.0.0
secret=1234
dtmfmode=rfc2833
canreinvite=no
context=from-internal
host=dynamic
trustrpid=yes
sendrpid=pai
type=friend
nat=yes
port=5060
qualify=yes
qualifyfreq=60
transport=udp
avpf=no
icesupport=no
encryption=no
callgroup=
pickupgroup=
dial=SIP/7500
[email protected]
permit=0.0.0.0/0.0.0.0
callerid=Shoaib <7500>
callcounter=yes
faxdetect=no
cc_monitor_policy=generic

i wnat to know is this the correct way.or i have to edit some other file

I know in the GUI it says that the secret needs to be atleast 6 characters long.

I have also tried with 6 or 8 characters but still d same.Actually i am confused whether editing is required in sip.config,sip_custom.conf or make a new file.