Between 10 min and 20 min after the specified strain has been reached, measure the strained reference length ( to the nearest 0,1 mm. When the inner diameter of ring test pieces is used as the reference length, it may be calculated from the diameter of the pulleys and the distance between them, measured to the nearest 0,1 mm. If the strain, calculated as specified in 6.1.4.1, does not conform to the appropriate standard value, taking into account tolerances, discard the test piece and prepare and test a replacement test piece with a modified applied strain