Credit to Ausdave for the photo in the main link. The deal is now live in-store.

Found this from Vooks.

3-day deal starting Boxing Day tomorrow at JB. Most likely an in-store promo only as it's not showing up online. In-store promo only

Nintendo eShop gift cards are available in $15, $30 & $60 denominations. They are used to purchase digital games for the Nintendo Switch (as well as other digital goods, such as subscriptions and DLC packs).