In this article on Adserver and Analytics Report Discrepancies, you’ll find the solution to the discrepancies between the Google Analytics and Adserver reports arising when measuring the ad campaigns.
Following an ad campaign launched by using Adservers, an addition to the destination URLs is sufficient. You can also track in Google Analytics how many clicks you received from which websites and which ad impressions.

With Google Analytics, we are getting data such as duration of visit, page views per visit and exit rate on the websites where ads are published, which normally we cannot get. In addition to this, if you are tracking conversion or e-commerce in Google Analytics, you can also track conversion and e-commerce purchase rates by the sources you are advertising.