A survey closed before the ‘close date’ in the invitation. Why?

In certain studies, we are required to set quotas within categories in order to obtain a picture that is representative of the general population. Once the number of completed answers is reached in a particular category, we are unable to accept any more answers, which is why the study will be marked as closed prior to the deadline of the survey. All the people who completed the survey before it is closed will be credited with points or contest entries. 

We try to invite the right number of people so that not too many will be prevented from answering.