When comparing Broadstreet reports with Google Analytics reports, you might have some level of discrepancy. But that usually suggests that the page is structured in a way that favors either Google Analytics or Broadstreet reports, which is difficult to avoid.
For example, if a page invokes analytics earlier (toward the head of the page), it gets executed before any ads load. So in that case, a page view is tracked before ad views get tracked.
It’s not unusual that scripts toward the top of the page get executed more frequently than those later in the markup. The browser might hang onto some external script, the user might stop the page from loading, or perhaps they’ve clicked to a different page before the page is fully loaded.
So there are a few different reasons for discrepancies, but Google Analytics running before ads do (or even after) is a common reason. You can also read up Google addressing that topic for DFP: https://support.google.com/admanager/answer/177405?hl=en