I'm having some trouble achieving the correct calculations with my order total modules.

We have a discount group that gets 3% off all orders.

I have set up a $10 coupon that is valid only on one product, with no minimum purchase.

If I restrict the coupon to the product, it calculates $10 minus the group discount, instead of applying the full $10.

Example:

Product A $10.00
Product B $1.00
Coupon restricted to product A

Order total shows:

Sub-Total: CDN $11.00
Group Discount - 3%: -CDN $0.33
Discount Coupon: wy487nwb: -CDN $9.67
Warehouse Pickup: CDN $0.00
13% Tax (ON): CDN $0.09
Total: CDN $0.76

Why is the coupon deducting the group discount from the coupon amount?

If I remove the restriction, the coupon applies correctly.

My order total modules sort order:
100 Sub-Total
102 Group Discount
103 Discount Coupon
200 Shipping
300 Tax
310 Gift Certificates
900 Total