Subscription discount codes take money off a paid membership plan at checkout. They live under Settings › Memberships & Billing › Subscription Discounts, separate from the promo codes you manage under Point Earning › Promo Codes.
1. The code fans will enter. Codes are stored in uppercase.
2. The subscription plan it applies to, or "any plan".
3. The discount amount in dollars.
4. A redemption limit, if you want one. Leave it out for unlimited.
5. The date the code is valid from.
6. The date it's valid until.
7. A payment maximum, if you want one — a cap on how much can be discounted on a single order.