Use the Commit CSV Export API to commit a specific csvGuid and take the related CSV as a new baseline for future delta exports. This means after this commit, the next delta export contains only those records in the KPIs that have been either added, changed, or deleted from the previous committed state.
The current version of a metadata configuration is available in the response of Checking Job Status. For example: "metaVersion": 8. If the underlying RTR Report Configuration record in a Salesforce org changes, then the previous commit is no longer valid for a delta export. A full export is scheduled next time.