Unfortunately, from time to time the clicks reported by your analytics platform and Broadstreet may not match up.
The issue here is that tracking referrals from redirected ad clicks is shaky at best. There’s a great a technical explanation here as to why that is.
It boils down to the fact that the way referrers are handled by various browsers was never specified by any authority. Different browsers might drop referral information or keep it depending on number of different factors. If the ad is opened in a new window, it’s almost always dropped.
There is a bit more information here as well about what could be happening.