According to Valorant Wiki there are 644 different skins, The amount of different Combinations of shop is 644 chose 4 = 7.1 * 10^9. The amount of permutations is 1.7 *10^11. (Combinations is where the order in which the skin appears doesn't matter and Permutation is where it does). So in this case to have this particular shop in one exact lay out is 1/170,000,000,000. But the probability just to have a certain assortment of items is 1/7,100,000,000.