The Excerpt settings under the source’s Advanced tab allow you to manage how excerpts are handled for the imported content.

Excerpt source
This setting determines how excerpts are created for imported items.
Options:
- Use the original excerpt: If the source provides an excerpt in its RSS feed, it will be imported and used as the excerpt on your site.
- Create excerpt from content: The plugin will create excerpts by taking the first set number of words from the content.
Aggregator also allows you to enable an option to create an excerpt if the original excerpt is missing from the feed source. This is especially useful when importing the original excerpts as some items may be missing an excerpt from the source.

Excerpt Length and Suffix
These option allows you to limit the length of the imported or generated excerpt.
- Length: Set the maximum number of words for the excerpt. For example, if you set this to 50 words, each excerpt will be trimmed to that length, even if it ends half way through a sentence.
- Suffix: Specify a suffix to be added at the end of the trimmed excerpt. By default, this is set to use ellipsis
…to indicate that the excerpt is just a snippet of the complete content.