Day 13 covers all of Chapter 8, The Assurance of Future Buddhahood of the Five Hundred Disciples.
Having last month heard from Pūrṇa about how extraordinary the World-Honored One is, we hear Śākyamuni praise Pūrṇa,
“Do you see this Pūrṇa, the son of Maitrāyanī? I always praise him, saying that he is the most excellent expounder of the Dharma. I also praise him for his various merits. He strenuously protects my teachings, and helps me propagate them. He shows the Way to the four kinds of devotees, teaches them, benefits them and causes them to rejoice. He explains my right teachings perfectly, and gives great benefits to those who are performing brahma practices’ with him. No one except the Tathāgata excels him in eloquence. Do not say that he protects only my teachings and helps me propagate them! In his previous existence he also protected the right teachings of nine thousand million Buddhas and helped them propagate their teachings. Under those Buddhas also he was the most excellent expounder of the Dharma. He clearly understood the truth of the Void expounded by those Buddhas, and obtained the four kinds of unhindered eloquence. He always expounded the Dharma clearly and purely, with no doubtfulness. Although he had the supernatural powers of Bodhisattvas, he performed brahma practices throughout his previous existence. Therefore, the people of the world of the Buddha I under whom he performed brahma practices] thought that he was a Śrāvaka. He benefited many hundreds of thousands of living beings with this expedient, and also caused innumerable, asaṃkhya people to aspire for Anuttara-samyak-saṃbodhi. He did the work of the Buddha, that is, taught all living beings so that the world of the Buddha might be purified.
Lotus World offers this on the topic of Pūrṇa and the major Śrāvakas:
“In the Lotus Sutra, the voice-hearers fall into three groups of superior capacity, intermediate capacity, and lesser capacity, depending on the manner in which they are able to understand the One Vehicle. Shariputra represents the superior category. He is able to understand the Buddha’s teaching of the reality of all things, the declaration of the One Vehicle in chapter two of the Lotus Sutra, and receives the Buddha’s prediction that he will become Flower Light Tathāgata in chapter three. Maudgalyayana, Mahakashyapa, Katyayana, and Subhuti comprise the intermediate category. They require the preaching of parables, such as the parable of the burning house in chapter three, in order to comprehend the One Vehicle. … Purna, Ananda, and Rahula represent those of lesser capacity. They must learn the One Vehicle in the context of stories of their past lives showing their connection to the One Vehicle before they believe that it applies to them. …”Lotus World: An Illustrated Guide to the Gohonzon