Changed the feed to show only excerpt

It seems that my feed become too big for Feedburner :), this is a standard issue, so I decided to show only the most recent 10 post in the feed, but strangely enough, wordpress ignore that settings and my feed continue to show latest 15 blog entry :(.

To keep the feed updated I decided to include only an excerpt in the feed, trying to understand how to tell wordpress to use only 10 latest posts for the feed. Until now, please excuse me if you have not the full content on the feed :(