[SOLVED] différent length of excerpts by posts

using : atahualpa 3.7.1
using;: WP 3.2.1
only on localhost, I began and i'm a novice in html, php, css ....!!

I want to post for a specific category in a sidebar. For this I use the plugin : " Category Posts".
I want an excerpt length for the posts on the main page and i want another excerpt lentgh in the post that are posted in sidebar
With this plugin("category post"), you can set the length of extract to display. it's ok with a theme like "twenty eleven. but impossible with Atahualpa.
With Atahualpa, the length of the extract to a post is the same in the main page and in the sidebar
where is the pb ?

Thanks