Question on tutorial: Build along create a text color reveal effect

Question:
It seems to me that the basis of this working is that the section is 1.5 times size of the viewport and the container is 1 times the viewport.
Also, the container is defined as sticky so as you scroll down the container covers the rest of the section that is greater than the viewport and it causes the scrolling animation occur.

It is basically working for me but there is a problem.
There always a little white blank area of the section that the container does not cover as it sticky scrolls…

Product:
Wix Studio

What are you trying to achieve:
How to make the sticky container go over the total empty part of the Section the is greater then the viewport.