
What happens is it lists all the possible classes, which with a puppy in theory is all the ones for his breed and sex, and also any stakes that apply.
As this is a rare breed or not separately classified and entries in lower classes are likely to be small, if it were me I would put him in Puppy Dog (PD) and Junior dog (JD) and Puppy stakes.
The latter will give him a chance to be in a large class with lots of different dogs in, as the first two are likely to be over with before he knows what is happening :D