Hi!
That section is usually just a space to add anything about your degree that isn't captured elsewhere in the application. A few things that you might include (and you don't necessarily need to include anything!):
- Any unusual aspects of your course (e.g. a year abroad, a dissertation, joint honours structure, or anything that makes your degree slightly different from the standard)
- Context around grades - if there is not a separate mitigating circumstances section, this could be a good place to briefly explain it
- Additional academic achievements (e.g. scholarships, awards, dean's list, prizes, or anything else related to your degree)
- Transfer of change of course - if you switched course or university at any point, this might be the best place to clarify
If you don't have anything you need to add, it's perfectly fine to keep it short / empty - they're just giving you an optional space in case something needs explaining.
Hope that helps, and best of luck with the Mills & Reeve application!