Adalysis will regularly check how many impressions active display campaigns show to a user on average.  If the number is more than 6 per day, it will alert you on the dashboard so you can cap the impressions. This will help improve your overall CTR as well as not frustrate some users.

You'll be taken to the view where only campaigns with high impression frequency are included.  Click on the icon in the Frequency Capping column to see the details. 

After that, you'll be able to set the impressions limit for each of your campaigns. A good practice is to cap it to about 5 impressions a day.