HRV requires a fair bit of data before it becomes meaningful. Take morning measurements (either automatic or Breathe triggered) for a month or so and look for patterns, relationships between workouts and HRV changes, etc. There are apps that do this for you, but they use the same underlying hardware as the health app. It will take time before you can make informed training decisions based on HRV, so patience is key. Don’t begin altering your routines based on only a week of measurements, because you’ll likely end up obfuscating important patterns and trends.