The Stages of Vipassana - 16th stage of vipassana nana

The sixteenth stage of vipassana nana is Reviewing knowledge (paccavekkhana nana).

When the magga-víthi-cittas have fallen away they are succeeded by bhavanga-cittas and then mind-door process cittas arise. These cittas review the enlightenment that was attained. In one process cittas review the magga-citta, in one process the phala-citta, in one process the defilements that have been eradicated, in another process the defilements which are still remaining and in another process again nibbana.
The person for whom the magga-citta and the phalacitta of the stage of the arahat have arisen, does not have to review the remaining defilements since the magga-citta of the arahat has completely eradicated all defilements.