The plug-in won’t reduce bounce rate; what it does (apparently - I’ve never used it) is ensure more accurate reporting of how long visitors to your site stay on each page. so that you have a better idea of how your visitors interact with your site.
So if visitors are arriving on a page, finding the information that they require, reading it and then leaving (having done what they wanted), you’ll be able to see that they’ve spent time on your site, rather than that being recorded simply as a “bounce”.