Changing RSS feed from full to summary, Safarica theme

I can’t figure out how to change the RSS feed length from full post to summary in the Safarica theme from Theme Forest. Mailchimp is showing the full post even though in reading settings I have chosen summary, and the RSS to email merge tags are correct in Mailchimp.
I know it is a theme issue because I have switched to the Twenty Twelve theme and Mailchimp was displaying the full post. Any thoughts would be greatly appreciated!
Elaine
http://www.fourhensandarooster.com