I'm getting serious errors in totals when using Gift Certificates:

Products in shopping cart: $45
tax (6%): 2.70
shipping: $1.30
subtotal: $49
Applied gift certificate: $10
total: $75.30

It apparently doubles the gift certificate value and adds the products in shopping cart total + shipping to come up with $75.30.

Am I missing something?

The GC module is configured as:
Gift Certificates

This module is installed
true

Sort Order
840

Queue Purchases
true

Include Shipping
true

Include Tax
true

Re-calculate Tax
None

Tax Class
--none--

Credit including Tax
false

Set Order Status
default

Thanks for your help!
-Peter