Day 13 covers all of Chapter 8, The Assurance of Future Buddhahood of the Five Hundred Disciples.

Having last month covered predictions for Pūrṇa’s future, today we hear from the twelve hundred Arhats.

Thereupon the twelve hundred Arhats, who had already obtained freedom of mind, thought:

“We have never been so joyful before. How glad we shall be if we are assured of our future Buddhahood by the World-Honored One just as the other great disciples were!” Seeing what they had in their minds, the Buddha said to Maha-Kāśyapa:

“Now I will assure these twelve hundred Arhats, who are present before me, of their future attainment of Anuttara-samyak-saṃbodhi one after another. My great disciple Kauṇḍinya Bhikṣu, who is among them, will make offerings to six billion and two hundred thousand million Buddhas, and then become a Buddha called Universal-Brightness, the Tathāgata, the Deserver of Offerings, the Perfectly Enlightened One, the Man of Wisdom and Practice, the Well-Gone, the Knower of the World, the Unsurpassed Man, the Controller of Men, the Teacher of Gods and Men, the Buddha, the World-Honored One. The others of the five hundred Arhats, including Uruvilvā-Kāśyapa, Gaya­Kāśyapa, Nadī-Kāśyapa, Kālodāyin, Udāyin, Aniruddha, Revata, Kapphina, Bakkula, Cunda, and Svāgata, also will attain Anuttara-samyak-saṃbodhi, and become Buddhas also called Universal-Brightness.”

Thereupon the World-Honored One, wishing to repeat what he had said, sang in gāthās:

Kauṇḍinya Bhikṣu will see
Innumerable Buddhas.
After asaṃkhya kalpas from now,
He will attain perfect enlightenment.

He will emit great rays of light [from his body].
He will have all supernatural powers.
His fame will spread over the worlds of the ten quarters.
Respected by all living beings,
He will expound unsurpassed enlightenment to them.
Therefore, he will be called Universal-Brightness.

His world will be pure.
The Bodhisattvas [of that world] will be brave.
They will go up to the tops of wonderful, tall buildings,
And then go out into the worlds of the ten quarters.
There they will make the best offerings
To the Buddhas of those worlds.

After making offerings, they will have great joy.
They will return to their home world in a moment.
They will be able to do all this
By their supernatural powers.

[Universal-Brightness] Buddha will live for sixty thousand kalpas.
His right teachings will be preserved twice as long as his life;
And the counterfeit of them, also twice as long as his right teachings.
When his teachings are eliminated, gods and men will be sad.

The five hundred bhikṣus
Will become Buddhas one after another.
They also will be called Universal-Brightness.
One who has become a Buddha will say to another:
“You will become a Buddha after my extinction.
[The living beings of] the world
To be saved by that Buddha
Will be like those whom I am teaching today.”

The beauty of the worlds [of those Buddhas],
And the supernatural powers [of those Buddhas],
And the number of the Bodhisattvas and Śrāvakas [of those worlds],
And the number of kalpas of the lives [of those Buddhas],
Of their right teachings, and of the counterfeit of them,
Will be the same [as in the case of Kauṇḍinya].

Kāśyapa! Now you have heard of the future
Of the five hundred Arhats
Who have freedom of mind.
All the other Śrāvakas also will [become Buddhas].
Tell this to the Śrāvakas
Who are not present here!

Reviewing this prediction, it’s applicable to consider this from Lotus Path: Practicing the Lotus Sutra Volume 1:

In the Lotus Sutra the Buddha assures us our ability to attain enlightenment! Nichiren established the most efficacious manner to carry out the practice of the Lotus Sutra: chanting Odaimoku – Namu Myoho Renge Kyo – assures us of manifesting our inherent Buddhahood in this very lifetime.

There are numerous predictions in the Lotus Sutra of future enlightenment of various people representing all the conditions of enlightenment. So no matter how we may view our present condition, the cause for enlightenment exists in this very moment within the phrase of the Sacred Title of the Lotus Sutra.
Lotus Path: Practicing the Lotus Sutra Volume 1