Jetpack Blog Subscriptions Settings

Hello!

I have a Govt Jobs blog. On my sidebar, I have a “Subscribe” option widget from Jetpack. I’d like to set it so subscribers receive summaries of posts with a link back to my site, rather than the entire post in the email. How would I do that? There seems to be no settings options. If I have to change something in the plug-in code, please give me detailed instructions as to which line and what to change. Thanks so much!