When there is a miinimum delivery fee the promo code being used doesn’t apply towards that. For example if someone has a $15 minimum delivery fee and there is a promo code used that drops the overall cart to $5 it will still allow the delivery to happen. The minimum delivery fee should be before tax, fees, promo codes etc. I believe it works properly on all other fees but the promo code will allow the delivery to happen even if there is a $0 cart value.