Formula milk guideline

Hi, I just started on breastfeeding for my newborn. As my supply is not enough, I was advised to mix feed and only require 30ml of FM per feed. I am using NAN and the standard guideline is 3 scoops to make 90ml. As I only need 30ml, can I just do 1 scoop each time or need to strictly follow and make 90ml but will waste 60ml?