The device itself takes measurements every 10 minutes and saves them. The data can then be downloaded with local access.
This is the voltage curve or power curve of each individual phase.
If you want it faster/more precise, you can read it out with HTTP GET. This then returns the measured values in JSON format for further processing/filing (that's how I do it).
There is an online documentation on this: https://shelly-api-docs.shelly.cloud/ and then select the [Gen Device 1 API].
Have fun.

With the standard Shelly app, I actually only see hourly gradations. But as far as I know, the device can do more. You just have to retrieve the data differently. That requires a little more knowledge.

That refers to the cloud, I think. I read it with FHEM and have implemented a query every few seconds. Runs without problems