Hi David H. Brown, Trim allowance is not the trim width. Usually, in a door,"trim allowance" means a the distance between the bottom of the door and the lower part of the trim. For example, in the image attached the trim allowance is 4". This is useful when you have an uneven floor Anyway, in your situation, the allowance is 0, this means that the trim and the door have the same dimension. So, the number you set in the Punch standard doors is the 3"or 4", and this value is the trim width Let us know if you need additional information Patricia