Follow the instructions below

Add the semicolon after the N, set the "Dial Delay Count" to 0 and the "Dial Delay Time" to 4 so that it forces the system to use the Dial Delay Time.

The Avaya documentation defines the use of the semicolon as such:

; - Receive Sending Complete

When used this must be the last character in the short code string. If the Dial Delay Count is 0, a ; instructs the system to wait for the number to be fully dialed, using the Dial Delay Time or the user dialing #, before acting on the short code. If the Dial Delay Count is non-zero, the dialing is only evaluated when # is pressed.

So it was the semicolon along with setting the Dial Delay Count to 0 that forced the system to use the Dial Delay Time. 

Problem sloved. The user no longer has to press pound to dial the number via the SIP trunk.