@MakeISgreatagainI have read all of your Posts and it is quite obvious that you still don't understand how the Promotion works...
So to Make it clear...
You have to First BUY 4 cards with Credits.
And after you BUY the 4th card, the Credits used to buy that card are Credited back to your Account.
You Wrote:
... and indeed, in case of the cashback, they are never spent, since the system give them before, so the amount of credits stay the same.
This is why I assumed it would worked. It looked logical.
The System Deducts the Credits First. If you Don't have enough Credits, the Purchase will not go through.
After the Purchase is Successful, the Card is Added to your collection, and the Credits Returned.
See you have to Buy it 1st, then the Credits are Returned.
I Have no Idea why you thought the system can put Credits Back in Before you Spend them. that is just not logical.