How to create a discount coupon programmaticaly in opencart 2.1.0.2

I have created a newsletter subscription pop-up using acumbamail and what i want is to programatically create a -10% discount coupon, which will last for 7 days, everytime someone clicks subscribe, then i will email the coupon code to the customer. I know that in opencart 2.1.0.2 you can go to marketing->coupons but i dont have the choice to create a coupon that lasts for 7 days from the day that the customer subscribed to the newsletter.

If you're not able to complete this task yourself, I'd recommend you to create a paid support request in Commercial Support section.

can you tell me at least how to get the coupons stored in the database?

"coupon" table.