I do not fully understand what your end objective is but it sounds like you're trying to silent the install from the end user. If you look in the delivery method there is an option to hide all feedback from user, this should make your install silent if that's what you're trying to accomplish. As for the error, it sounds like you have your delivery method set for some type of feedback but your command line set for quiet. So in a sense you are asking it to do two things that conflict with each other.
Hope this helps