The text expand icons can show up for many reasons.
Most likely it's because there is hidden text or formatting that while you can't see it, is affecting the number of characters it takes for Captivate to detect that there is too much text to display. There could be formatting, or a series of extra line breaks that at a glance you don't see but are there. Edit the text for these elements and press CTRL+A to select and highlight the text. You will quite clearly see extra line breaks if that's it. When adding text always either make sure you paste it in without formatting or use a tool like PureText to strip out any formatting from Microsoft Office or wherever you are copying your text from.
Another reason they show up is that you've applied an effect to these items such as an Ease-In or something like that. This is bug and you should take the time to report it.
It doesn't look like it in this case, but some fonts use up way more space than the visible character itself. I don't think this is the case, because that looks like Trebuchet MS, but something to be aware of
Paul Wilson, CTDP