Define window for vertical scrolling text

[LindaL]

When scrolling text, I have 20 lines of text but only want to display a maximum of 4 lines of text. How do I define the window for vertical scrolling text? Thank you.

[borate]

Clip length affects the speed:  longer = slower.  A speed change can be applied, but results may not be optimal.

Here's 30" of video with 30"of text, composed with blank lines between each entry...