Google Analytics counts all the events and actions from a particular user in a single session as one single unique event or goal. So, if a user signs up for the newsletter three times in three separate sessions then Google Analytics will count it as 3 goal conversions. If the user would have signed up three times in one session then it would have counted as only 1 goal conversion.
This question is a part of the Google Analytics Individual Qualification. You can get all the answers with detailed explanation for this exam in our Google Analytics Individual Qualification Exam Answers page.