The larger the sample size, the more reliable survey findings are.  A survey based on 500 people is more reliable than one based on 50.  Usurv therefore automatically highlights when a survey (or a group in a survey e.g 18-29 year olds)  is based on a small or extremely small sample size.  Small and extremely small sample sizes are based on the following definitions:

Small sample size: under 50 respondents

Extremely small sample size: under 30 respondents