If you perform a quantity increase on a subscription + redeem a coupon while performing the quantity increase:
Quantity increases result in a charge for the quantity difference, so the coupon discount would apply to the additional quantity that is added during the upgrade, not the entire subscription.
Let's say halfway through a monthly billing period subscription to Gold with 5 users is increased to 7 users and each user price is $10. You also decide to add a fixed-price coupon for $10 off.
We get a charge with $0 because:
- 7 Qty - 5 Qty is 2 Qty
- Normal price per user is $10.00
- Proration is 50% due to timing of change
- Price prorated is $10.00 x 50% = $5.00
- $10 off coupon is applied
- 2 Qty x $5.00 Prorated Price - $10 off coupon = $0