When you extract a report using AdWords API, you have to keep in mind that the reporting data is not real-time i.e. there is a
certain lag between the occurrence of an event and the event data being available via the API. In other words, when you use a date predicate (such as YESTERDAY) in your API report to filter the results, depending on when the report was run, there might be some records which are not yet available in the report. Also, when trying to compare a UI report with the API report, please ensure you have
exactly the same filters applied at both places.