From a broken scale, measurement can be done from zero mark.
Suppose you had to make some measurement and the only scale you had broke off. Think whether while using a meter/centimeter scale, it is okay to take measurements from some mark other than zero.
The zero mark of a ruler is broken and the length of a box is measured from 2 cm mark of the ruler. The length is found to be 20 cm. What is the actual length of box?