"How to delete everything Alexa ever recorded in your house"- BGR

"Each of the items that appears is a different time that Alexa has been triggered. If Alexa recognized what was being said to her, the text of what you said will show up. If she doesn’t understand what was said, it was likely a false triggering (Alexa misheard something else you said as “Alexa”). However, Amazon still stores the audio recordings of those false triggers, unless you use the app to delete that recording." - Chris Mills