Form e can't display whether fully domestic wo has any impac

We exported a batch of machinery and equipment to Vietnam, and the customer asked to provide form e certificate of origin for customs clearance, so we proposed to find a trading company to handle a form e certificate of origin. However, our factory also went to the commodity inspection bureau to learn about it before, because all our materials are domestic, so form China made wo can be displayed in column 8 of form e certificate of origin, but our agent company said that because we export mechanical equipment products, column 8 of form e certificate of origin can only show percentage, but not completely domestic wo. Can we ask if the completely domestic Wo cannot be displayed on form e certificate of origin, does it affect customers?