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

Having last month covered how Sakyamuni’s disciples are performing the Bodhisattva practices secretly, we hear of Purna’s past efforts.

Under hundreds of thousands of millions of past Buddhas,
This Purna practiced strenuously what he should do.
He expounded and protected
The teachings of those Buddhas.

In order to obtain unsurpassed wisdom,
He became the most excellent disciple
Of those Buddhas.
He was learned and wise.
He expounded the Dharma without fear,
And made his listeners rejoice.
He was never tired
Of helping those Buddhas do their work.

He obtained great supernatural powers
And the four kinds of unhindered eloquence.
Seeing who was clever, and who was dull,
He always expounded the Pure Dharma.

He expounded the dharma of the Great Vehicle
To hundreds of thousands of millions of living beings,
And caused them to dwell in the Dharma
So that the worlds of those Buddhas might be purified.

To underline this idea of causing listeners to dwell in the Dharma so that the worlds of those Buddhas might be purified, I offer this quote from Lotus Path: Practicing the Lotus Sutra Volume 1:

Sometimes uncovering or showing a small part of something enables us to see the potential of something even greater. Protecting something that is small or encouraging a fledgling effort can result in unimaginable outcomes. As our lives are slowly freed from illusions and then our eyes purified we are able to see the truth in the sutra, the truth in our lives and become Buddhas.

It might be eye opening for you to actually make a list of improvements in your life, both big and small, since you began practicing Buddhism.
Lotus Path: Practicing the Lotus Sutra Volume 1