Well formed hints/explanatory notes might be helpful to ensure a higher response rate and better data quality.
1. Open the survey builder and find the question you want to edit. Click Edit.
2. The second box right under the question title is the extra description. If you don’t want to enter any extra description, simply leave the field empty. 
Tip: The extra description can be an important part of the questions in a survey, especially when using more complicated instructions or question types etc. You can inform the respondent how exactly you want the question to be filled-out. E.g. “Choose more than 2 options”, “Explanatory notes: 1 - excellent, 2 - good , 3 - sufficient, 4 - bad, 5 - very bad”.