Understanding the Compare to Previous Feature in Mixpanel

Hi fellow Mixpanel users. I am trying to understand “Compare to previous” feature in Mixpanel. Do I compare to an average during the previous 30 days or to a single day value 30 days ago? Here i select an event that happened today hour by hour and compare it to a “previous 30 days”. Then this doted line is an average of hours for the last 30 days, or it is hour by hour a day 30 days go compared to today? Thank you for your help! 🙂