we will do a random roll (based on the block id of block #30,000,000) to see if you would have gotten one of these cards. If you would have, then you will receive one in the airdrop.
Writing purchased packs are raffle tickets for airdrop would be more accurate, it seems.
From one of the comments:
random number generator that isn't known until that block is reached and the hashes of the blocks are used to seed the random number generator
Thus hash will be the source of a new seed for (pseudo) random generator, thus one will be rolled different cards than received in the past. Also, no cards will be taken, so lucky one will get one or a few more cards than would have if they were included from the beginning.
In short - we cannot repeat random lotteries, as drawing each next card should be independent from what cards have been drawn before.