Here are a few ways you can understand what data a connection synced (or didn't if encountered an issue), and understand the underlying source and sample a measurement was created from.
Each measurement created from an Apple Health connection has meta information about the underlying source, sample, timezone and query. To view, open the appropriate Measure and click on the "Meta" icon or "Details" on the "•••" button.
Connection Debug Details & Logs
You can view the debug details of a connection and it's sync logs. View the connection by in the app going to Settings, then Apple Health, then tapping on the connection. Then tap the "•••" button and select either "Show Debug Details" or "View Debug Logs". You can tap a log to view all the sync details.