You may find inconstancies with Google Analytics data in Chartio. The main reason for this is the fact that Google Analytics samples their data (See Google documentation on data sampling for more information). Depending on what Google Analytics account you have, you may be limited to sampled data. Only the premium accounts support unsampled data.
However, the numbers should still be fairly close - sampling is meant to give you a close approximation.
It seems the sample data is fairly accurate when it comes to visits and page views but can vary in a wide rage for revenue, transactions, and goal conversions. In one of the tests from the articles below, they found revenue could be off by 11% to 80%.
There’s a number of articles you can search for on Google.
- Can you trust your Google Analytics data?
- Data Sampling in Google Analytics: How It Works, Why It Matters, and What to Do About It
To get unsampled data would require a Google Analytics premium account and BigQuery.
We currently use Google’s Core Reporting API V4. You may be able to return more accurate results by using:
More information on Reporting API V4
Additionally, you may be able to pull unsampled data using other various techniques, such as this technique, Pull More than 10k rows Unsampled using Google Analytics Sheets Add-on.