The 3rd case-affix is used after the words denoting the duration of time or place, when the accomplishment of the desired object is meant to be expressed.,
मासेनानुवाकोऽधीतः 'he learnt the Anuvaka in a month,' क्रोशेनानुवाकोऽधीतः 'he learnt the Anuvaka by going over a kos.
The word अपवर्ग means 'the finishing of an action, on the attainment of the object intended by the action, but not before.' Thus संवत्सरेणानुवाकोऽधीतः means 'Anuvaka was persaveringly and effectually read by him in the whole year.'
When the idea of apavarga is not intended, the accusative case is employed, as मासमधीतोऽनुवाकः 'learnt for a month, but not yet completed, the Anuvaka.',