Hi @dave8 ,
The 'API calls per connection' is 20 means that you could send 20 HTTP Request calls at most to your Excel file from your canvas app in one minute (through per connection).
Actually, PowerApps canvas app inherits data access permission from data source itself. If there are multiple users (> 2) updating data within your Excel table simultaneously, they may face a Conflict Update Error on their side.
In addition, when you open your Excel file in web browser, you could not update the data within your Excel table due to File Lock mechanism.
Note: Actually, when you made changes to your Excel table using built-in functions in canvas app, it essentially send a HTTP Request call to your Excel file.
If you want to verify the number of API calls occurring in this App with Excel Online connector, I afraid that there is no direct way to achieve your needs. As an available solution, you could share your canvas app to 21 end users, and share your Excel table to these users. And then ask them to run your app, and add new entry, then click "Submit" button simultaneously, then check if the throttling limit error would show up.
Note: Actually, the API calls limit is specified within the Rest API supported for the Excel Online (Business) connector. Currently, we could not change this limit
Best regards,
