Please explain

It is just the balance of your service credit. For example, when you order an annual subscription, let's say $199.99/year subscription, it will charge your credit card for $199.99, then deposit the money into your DriveHQ account as Service Coupon Balance. Then the first month service fee is deducted from the Service Coupon Balance. So right after you order, your remaining Service Coupon Balance is about $183. ( The real amount can be bigger if you don't order the subscription right after you sign up the free service. This is because your billing date is the day-of-month when you sign up DriveHQ membership. )

Service Coupon Balance is used mainly for internal billing purpose. Each month DriveHQ deducts your service coupon balance for the amount of monthly fee. This is useful when you upgrade your service. For example, after 6 months, you want to upgrade your subscription, you can order a new subscription and cancel the current subscription. You will not lose any un-used credit.

Please also note DriveHQ never automatically debit your credit card / PayPal. We don't keep your billing info on file. So you need to make payments manually. To avoid the hassle, please pay several months at once, or pay annually.