Prioritize Eligible Courses is a way to adjust your requirements if a course would normally be filling a different requirement, and you’d rather prioritize it elsewhere. It is important to note that this is not an exception - "prioritize eligible courses" can only be used if the course already satisfies the constraints of the requirement. (To instead see how to request an exception, please visit this article.)
In the example below, Calculus III is a course that is permitted to fulfill multiple categories of the requirements. This can be noted by looking at the requirements of both categories within the audit, or by clicking on the course and seeing the "counts for" in the course sidebar. Since you can only use the course for one category, Stellic automatically places it into one of the requirements. The exclamation point icon here tells us that Calculus III or Differential Equations could be used for the requirement Math Electives, but is being used for a different requirement instead.
If you would rather use the course in a different category, you can move it using the Prioritize Eligible Courses functionality (if allowed by your institution). To move the course to this requirement, select the dotted menu icon at the requirement level. This will generate a prompt asking to specify the course to be prioritized (note, this will only accept courses that are already permitted to count for the requirement), and also requires a justification.
Once the prioritization has been submitted, it shows successfully with a green checkmark in the preferred requirement. You can also see a green "1 prioritized courses" note on the requirement that was just adjusted. Clicking on the green "1 Prioritized Courses" icon will give further details about the prioritization, and clicking the details of that will give you the name of the person that inserted the prioritization, along with their justification.