Data size difference between API call result and UI download

[LEXQ2005]

I want to get data from a company’s internal app. The app offers download to a CSV, as well as API Query (JSON Script).
When I use JSON API call, I get 40K rows of data in the output. While I download to CSV from app UI, I get 70K rows of data.
What can be the possible reasons that cause the difference?
Do the data pools API and download method connect to are different?

[MatthewO]

@LEXQ2005 many APIs are designed with pagination which limits the number of records returned from a single request. Imagine if the data set you requested had 10 million records, it could be too large to transmit in a single GET request. The API documentation should tell you what the offset is so that you can properly structure your requests. You could also build an iterative macro to make the API requests until all of the data is retrieved. An example is available in the following post: https://community.alteryx.com/t5/Alteryx-Designer-Discussions/Iterative-macro-for-API-pagination-ret...