[Plugin: WP-UTF8-Excerpt] Number of characters in excerpt

I think my theme is using this function to generate excerpts. But I couldn’t find how to increase its length.

if (get_option($shortname.'_use_excerpt') == 'on' && $postExcerpt <> '') {
		if ($echo) echo $postExcerpt;
		else return $postExcerpt;
	} else {
		$truncate = $post->post_content;

		$truncate = preg_replace('@\[caption[^\]]*?\].*?\[\/caption]@si', '', $truncate);

		if ( strlen($truncate) <= $amount ) $echo_out = ''; else $echo_out = '...';
		$truncate = apply_filters('the_content', $truncate);
		$truncate = preg_replace('@<script[^>]*?>.*?</script>@si', '', $truncate);
		$truncate = preg_replace('@<style[^>]*?>.*?</style>@si', '', $truncate);

		$truncate = strip_tags($truncate);

		if ($echo_out == '...') $truncate = substr($truncate, 0, strrpos(substr($truncate, 0, $amount), ' '));
		else $truncate = substr($truncate, 0, $amount);

		if ($echo) echo $truncate,$echo_out;
		else return ($truncate . $echo_out);
	};