How to select a proper value for zone_size argument of the upload_progress directive?

Server NGINX
#1

How many simultaneous uploads I can track with zone_size set to 1m?

Is it a total amount of memory which server allocates per zone or per
upload?

Thanks for any help.

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,228498,228498#msg-228498