I've never heard of UV@100%, are you sure this wasn't a custom calculated metric set up by someone in your organization? Can you share a screenshot of where you are seeing this?
You can use out-of-the-box 'Unique Visitors' metric as it shows the number of visitor IDs for the dimension value.
Document Reference for a detailed insight:
Metric UV@100% appears to be a calculated metric created by some user in your organization.
Hope this helps!