The difference in the total amount purchased by a customer with a gift card vs. the value on the card they were using, over the life of the card or until the card balance goes to zero (for reloadable cards).
Here is an example,
A customer has a new gift card with $100 in funds on it. Next, they visit your store and makes a purchase for $50 (no lift yet). On a subsequent visit, they make a purchase of $70. The lift generated by that card would be 20% (or $20).
NOTE: Lift can only be calculated if your implementation is set to pass us the full requested order amount for a transaction. Contact us at firstname.lastname@example.org for information on how to enable this.