There’s a few different factors that are likely contributing here which I’ve outlined for you below.
As a heads up for future reference, the best way to receive support for questions related to product functionality such as yours will be to reach out to Stitch’s support team through in-application chat or via email at email@example.com.
Most of Stitch’s ad-reporting integrations such as Facebook Ads and Google Analytics or Google Ads use a conversion window in order to capture changes made to data within the source account over a given period of time.
This functionality will always be listed in Stitch’s documentation for a source where it is used, such as in this section for the Google Ads integration, and for this data source specifically, Stitch uses a 30 day conversion window for any reporting tables, so you would see the past 30 days worth of data extracted and loaded during each replication cycle.
Append-Only Functionality of Google Ads
In the case of the Google AdWords integration, it’s also worth noting that any report tables replicated will always function in an append-only manner, regardless of the destination you’re using.
This is outlined in more detail in the page linked above for the Google Ads documentation, and while this functionality is not configurable, you can find some more information on approaches for accounting for this duplication and grabbing the latest version of each record from this page of Stitch’s documentation, or this page dedicated to querying append-only tables.