User ID is used to tell Site Analyzer how to recognize the User ID field in the log record.
Resolving the problem
Based on your choices, Site Analyzer will search different parts of a log record such as a cookie string, query string, the URL stem or a custom User ID field. After you define the location of the User IDs, sort your choices so that Site Analyzer can begin searching for a match. Once it finds a match, it discontinues searching.
Create a project for each User ID in which you want to define. Therefore, if you have 2 key names (aud= and id=) create two projects. Define one User ID in each project.