The plastic limit of a soil is the lowest water content determined in accordance with the following procedure at which the soil remains plastic. The plasticity index of a soil is the range in water content@ expressed as a percentage of the mass of the oven-dried soil@ within which the material is in a plastic state. It is the numerical difference between the liquid limit and plastic limit of the soil. The following applies to all specified limits in this standard: For the purpose of determining conformance with these specifications@ an observed value or a calculated value shall be rounded off ??to the nearest unit?? in the last right-hand place of figures used in expressing the limiting value@ in accordance with R 11. The Hand Rolling Method shall be the referee procedure.