When the app takes a gift card payment, it has to create a separate sale in your Lightspeed Retail account to debit the card. You'll note AdVision created a new product in your LSR for gift card payments. Please don't modify or remove this product, it's needed for the app to charge the appropriate amount to gift cards.
To use gift cards, you just have to create them in your LSR account, then you can use the code in the payment page. https://retail-support.lightspeedhq.com/hc/en-us/articles/228842287-Selling-and-recharging-gift-cards