Received an email from Delta today with this offer: "For a limited time, give the gift of travel and earn 4X miles per dollar spent when you spend $250 or more in Delta Gift Cards. The Delta Gift Card can be used to go anywhere Delta flies and on any Delta Vacations® package with airfare."

So how does this work? Let's say I buy a $1000 Delta gift card for myself which I can use later to purchase $1000 in Delta travel. I understand that.
1) But they're going to give me 4,000 miles for just buying it?
2) When I actually take the trip, I still earn miles for the trip?
3) If I pay for the gift card with my Delta American Express Reserve credit card which earns 3X miles on Delta purchases, I earn another 3,000 miles?

I just can't get this through my head, lol.
Am I missing something here?
Thanks!