Sent Gift card at a specific time: Shopify offset variable in Recipient form

[VictorCQ]

Now, I want to choose a specific time for sending gift cart in Recipient form. I saw a variable__shopify_offset in Dawn theme which I tried to set a time. Although it's not in document but it's work for me. However It's not sent at a specific time but also it sent in a time range and I don't really understand the way it work.

https://shopify.dev/docs/themes/product-merchandising/gift-cards

• Recipient email: The email address that the gift card will be sent to.
• Recipient name: Optional. The name that the gift card will be addressed to.
• Message: Optional. A message that can be included in the gift card email.
• Send on: Optional. The date in ISO 8601 format that's used to schedule sending a gift card. If you don't specify a date, then the gift card is sent immediately.
• __shopify_send_gift_card_to_recipient: A property that needs to be included with the value true to validate and process recipient information.

Do you the purpose of this variable (variable__shopify_offset) and the way it work?

If anyone know the answer or have the experience at this case, please share it with me. Thank you so much.