Coupon

1: Setup Discount Amount:

Only insert the amount of input or the percent of input.

2: Customize field for this tab

You can customize template in child theme:

Copy file 
wp-content/plugins/eventlist/templates/vendor/__edit-event-coupon.php 
to
wp-content/themes/meup-child/eventlist/vendor/__edit-event-coupon.php
and edit code in that file