In the beginning of the campaign we awarded Day1 Cards and Milestone Cards to people who backed during the campaign at certain times. Milestone cards came in during the campaign when we were day 1, hit 50%, 75%, and 100% funding. (They are all exclusive to one very short limited print run. After we run out, we won't print any more of them!)
Because some felt we were penalizing those who didn't back early and were upset about missing these cards, we offered an Add-on for singles of cards they missed. I actually hadn't thought about it being considered a punishment to new backers, rather a bonus reward to people who backed.
So to make things more welcoming, we are giving away all milestones unlocked, to everyone who backs the campaign (but not for the pledge manager afterwards). And if you you want additional milestone cards or backer cards, you can still add them with the exclusive pack and exclusive singles pack.
Currently, as I type this, for adding an Exclusive Pack, you will be receiving 68 cards (5 milestones and all backer created cards with the exception of the character decks/overpower cards) in that Exclusive Pack. As more backers come on board and create cards, that number will go even higher.
The add-on for the Exclusive Single Card was originally was tailored for anyone who came in later who missed the Day1 Cards and just needed 1 or 2 of them. Now that we are making them available for everyone, the sole purpose is for anyone who created a card who wants multiple copies of their own cards without having to get an entire Exclusive Pack just to get one card :)