In the Audience tab of the survey builder, you can choose the demographics (including quotas) that you want to send your survey to. 

This will ensure that only respondents matching those chosen demographic profiles screen into the survey. Some respondents might have already filled out this information on a previous survey, while some will be asked for it for the first time. 

If you did not choose to send your survey to a select audience, the additional demographic details you see on your results dashboard (right hand side), that you didn't request, we give as added value. However, not all of your respondents will have submitted these extra details, if they haven't completed a survey before that requires extra demographic details and you did not ask for them. This means that some of these additional demographic filters might not add up to 100%, if not all respondents have mapped this data. 

Demographics such as gender and home region are commonly used, so most respondents will have these mapped, while other demographic details are less commonly asked in surveys and so less frequently mapped. 

We display the demographic information for the respondents we do already have mapped, in case it generates valuable insights for you, but it has no impact on the demographics you have personally chosen for the survey.