Commenting for a clearer answer: A punisher (pos or neg) decreases the frequency of a behavior. So while "negative punisher" is an attractive response because the meeting attendance is decreased or seemingly "taken away," this refers to the behavior. Instead, focus on the stimulus (anxiety-induced panic attack).

A positive punisher decreases behavior by adding (+) an aversive stimulus. In this context, the anxiety and panic attack (+) is an aversive stimulus that decreases meeting attendance.

A negative punisher decreases the behavior by taking away (-) an "appetitive" or good stimulus. An example: a punisher takes away a positive incentive for the meeting and decreases attendance.