Should a woman whose waiting period (iddah) coincided with the first three months being 29 days and the fourth month being full, complete her iddah by adding only ten days or thirteen days?

The iddah (waiting period) for a woman whose husband has passed away is four months and ten nights. It begins from the moment of the husband's death and ends upon the completion of this period, based on the Almighty's saying: (وَالَّذِينَ يُتَوَفَّوْنَ مِنْكُمْ وَيَذَرُونَ أَزْوَاجًا يَتَرَبَّصْنَ بِأَنْفُسِهِنَّ أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا) "And those of you who die and leave wives behind - they, [the wives], shall wait concerning themselves for four months and ten [days]." The duration is calculated using lunar Arabic months. If the death occurs at the beginning of the month, then four full lunar months are counted, and ten days are added from the fifth month. However, if the death occurs during the month, then she observes the iddah for the remainder of the first month, three months by sighting the new moons, and ten days are added. The remaining period from the first month is counted to correspond with the same day number of the month in which the husband died in the fifth month. This is the preferred view of Ibn Taymiyyah and Ibn 'Uthaymeen.