It is all about user Interface. There is no way to keep it clear and provide tons of features and controls at the same time. We do not want to turn our app into a mobile data analysis platform.
If you need to dive deeper into analysis all your gathered data always can be exported in basic CSV format. Download example.
Data is stored on the device for the last 5 days for the PLUS model and 10 days for PRO. On a smartphone, the data volume is limited only by the free space in the storage. The smartphone will have all the data if you synchronize more than once every 5 or 10 days respectively. Synchronization starts when you connect to the device through the application.