You may find inconstancies with GA data in Chartio. The main reason for this is the fact that GA samples their data https://support.google.com/analytics/answer/2637192?hl=en. 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. Here’s a couple I like:
To get unsampled data would require a GA premium account and BigQuery: https://cloud.google.com/solutions/google-analytics-bigquery
We currently use Google’s Core Reporting API V4. You may be able to return more accurate results by using:
See this link for more information: https://developers.google.com/analytics/devguides/reporting/core/v4/rest/v4/reports/batchGet#sampling
Additionally, you may be able to pull unsampled data using other various techniques: http://www.ryanpraski.com/google-analytics-sheets-add-on-unsampled-data-more-than-10000-rows/