yeah they have it set up weird... i wouldnt say the 15s are useless, the gym i train at had no 15s for a while, it was a pain in the ass lol i use 15s all the time now that we have them.
but as for their set up its odd, once you drop each small plate so theres only a pair of each, with 2 of the 10s and the 2 15s (if he decides he doesnt want them), you have 67.5, so even if you got them to make up the 60 in 20s, its 3... and you need the small plates to make up the 7.5, and even still then once you make it up you will have 3 2.5s and 5s lol dafuq