Re: How do I retrieve a report with data having more than 10 rows using the External API?
You can pass the max_groups parameter to specify the number of groups you would like to be returned. As of now, the default is set to 10 rows. There isn't one special value to use in order to return all rows, so I suggest setting max_groups to a large number that you're sure will contain all results. I find it helpful to run the query in the UI so I can explore the size of the result set a bit, then use that to come up with a good number for max_groups.
Here is a good doc which talks about all the parameters and its default values: