Percent of Network Requests is the % of network calls we've received that have been classified as first-party. It's not exactly a performance metric but is valuable to look at as sudden changes can be interesting. This metric is included on the Version Comparison dashboard by default or can be added to a custom dashboard.
For example, if there is a sudden spike in % upward, it may mean that more calls have been classified as first-party, or that your API has suddenly been hit more often. Similarly, a sudden drop may mean a spike in calls from a third party.
To learn more about how to create custom dashboards, reference this guide.