Hi,
Well. You could create one coupon and then use the copy button on the coupons listing to duplicate it, then duplicate it and the copy, etc until you get enough of them.
Another solution is to create a coupon, export it with the "export" button of the coupons listing, then open the CSV file with Excel or Calc and generate the rest of the rows by duplicating the one of your coupon using the tools of the Excel/Calc.
Then, import back the CSV file in the table hikashop_discount via your PHPMyAdmin.