If you are using a multiple call group and set the system call forward template, then it will go to voicemail based on the system timer.

I just mention this because if you set delay 1 to 8 seconds, it may go to voicemail before the delay ringing kicks in.

I like to keep the SCP blank and just put the voicemail pilot in the MCG table as delay 2. That gives better flexability on when the call goes to voicemail, if I need more time. Other techs at my company always ask why I do it this way.