Mike,
Didn't realize that wasn't configurable. We originally envisioned it being so, but didn't add the option. For doing it manually, you just need to edit the /plugins/content/jfbcconent.php file. Search for 100, and you'll come up with the line below:
$articleText = substr($articleText, 0, 100);
Change the 100 to whatever value you want.
I've added this as a task, and it will likely be in the next release (after 4.1.2, which is due out later today or tomorrow).
Thanks,
Alex