This article discusses the connect percentages displayed below the Call from number.  

Users making outbound calls often strategically choose the Call from the number they dial to increase the prospect's likelihood of picking up. They may be trying to match the area they’re calling into or using a number that’s not showing up on caller IDs as “Spam likely”, “Telemarketer”, or “Other business name”. 

The Call from number drop list now helps reps decide which numbers are effective prospects when dialing prospects by showing the connect rate along with highlighting which number has the potential has been flagged as spam on caller IDs.