@svoelker: I don’t know which slider you are using. There is option for post slider, image slider and others.
If you are using post slider, then you can adjust the amount of text from the excerpt box in your post. See this http://en.support.wordpress.com/splitting-content/excerpts/
If you are using Image Slider, then you can change the content from the slider options itself.
If you want to adjust the width of the slider text box then you can add the following css in “Appearance => Theme Options => Custom CSS” box.
/* For Screen Size above 960px */
@media screen and (min-width: 960px) {
.featured-text {
width: 80%;
}
}