Question
What is the difference between Current Audience Size and Unique Visitors under Website Audiences?
Answer
Current Audience Size is the number of unique visitors in a segment based on segment duration in days. This is the total number of visitors who can be targeted using this segment.
The Unique Visitors is the number of users who were tracked during the particular date range selected in the dashboard date-picker at the top.
Check out What are Audiences? to learn more.