Day 15 concludes Chapter 10, The Teacher of the Dharma, and opens Chapter 11, Beholding the Stūpa of Treasures.

Having last month concluded Chapter 10, The Teacher of the Dharma, we behold the Stupa of Treasures.

Thereupon a stupa of the seven treasures sprang up from underground and hung in the sky before the Buddha. The stupa was five hundred yojanas high and two hundred and fifty yojanas wide and deep. lt was adorned with various treasures. It was furnished with five thousand railings and ten million chambers. It was adorned with innumerable banners and streamers, from which jeweled necklaces and billions of jeweled bells were hanging down. The fragrance of tamalapattra and candana was sent forth from the four sides of the stupa to all the corners of the world. Many canopies, adorned with streamers, and made of the seven treasures-gold, silver, lapis lazuli, shell, agate, pearl and ruby were hanging in the sky [one upon another from the top of the stupa] up to the [heaven of the] palaces of the four heavenly-kings. The thirty-three gods offered a rain of heavenly mandārava-flowers to the stupa of treasures. Thousands of billions of living beings, including the other gods, dragons, yakṣas, gandharvas, asuras, garuḍas, kiṃnaras, mahoragas, men and nonhuman beings, also offered flowers, incense, necklaces, streamers, canopies and music to the stupa of treasures, venerated the stupa, honored it, and praised it.

Lotus World offers this on the arrival of the Stupa of Treasures:

The jeweled stupa arising from the earth represents the emergence of Buddhahood (the stupa) from the ground of Buddha-nature in people’s ordinary lives (the earth). The transformation of this world is a graphic reminder that this world is the real pure land where enlightenment actually occurs. The recall of the emanated Buddhas from the pure lands reveals that these idealized Buddhas are personifications of the enlightened qualities and inner life of the historical Shakyamuni Buddha. The image of Many Treasures Tathagata and Shakyamuni Buddha seated together symbolizes the unity of the true reality of life and the wisdom of the person who awakens to reality.Lotus World: An Illustrated Guide to the Gohonzon