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

Having last month covered the prediction of Purna’s future Buddhahood and the nature of the world of that Buddha, we consider how Sakyamuni’s disciples are performing the Bodhisattva practices secretly.

Bhisus, listen to me attentively!
The Way practiced by my sons
Is beyond your comprehension
Because they learned how to employ expedients.

Knowing that people wish to hear
The teachings of the Lesser Vehicle,
And that they are afraid of having the great wisdom,
[My sons, that is,] the Bodhisattvas transform themselves
Into Sravakas or cause-knowers,
And teach the people with innumerable expedients.

Saying to the innumerable living beings, [for instance,]
“We are Sravakas.
We are far from the enlightenment of the Buddha,”
They save them, and cause them to attain [Sravakahoodl
Even the lazy people who wish to hear the Lesser Vehicle
Will become Buddhas with this expedient in the course of time.

My disciples are performing
The Bodhisattva practices secretly
Though they show themselves in the form of Sravakas.
They are purifying my world
Though they pretend to want little
And to shun birth-and-death.
In the presence of the people,
They pretend to have the three poisons and wrong views.
They save them with these expedients.
They change themselves into various forms.
If I speak of all their transformations,
The listeners will doubt me.

The Daily Dharma from Aug. 11, 2016, offers this interpretation:

My disciples are performing
The Bodhisattva practices secretly
Though they show themselves in the form of Śrāvakas.
They are purifying my world.