When asking a question using the scale response type (1-7), the default labels are 1 = very low, and 7= very high.
You can change this to suit your question context, simply select the Scale response type and write your own labels in the text fields with the edit pencil 
below the numbers (1) and (7).
This quick video shows you how:
Note that template questions have updated scale labels to suit the question, so you won't need to customize these labels.