When setting up a post module, you can choose to display the content in full or an excerpt. WordPress automatically displays the first 55 words from the post content and add [...] at the end. But what if you wanted a shorter excerpt? You can set this up by editing the specific post. By default, the excerpt panel is hidden. You can turn it on by clicking on the "Screen Options" located in the top right corner and then checking the "Excerpt" checkbox. The Excerpt panel will appear at the bottom.
Type in exactly what you want displayed as the excerpt. Note that you cannot add any HTML tags to the excerpt.