the 23 card pack is made of 2 out of 4 possible 11 cards lines, one of those lines is based on which of the 4 promos is in the pack, the other is one of the other 3 possible
ie 4 promos (listed as a, b, c, d) 4 lines of 11 cards (listed as A, B, C, D)
pack with promo a will have line A and either B, C or D)
b will have B and either A, C or D
etc..
so its semi random in that there are 12 different combinations