Bava Kama pg 22

In Bava Kama pg 22 I am wondering why when the we say the dog with the loaf and coal cause a stack to get burnt up that is the “arrows of the dog” and so obligated only for half damage, but on the same page when the camel loaded with linen goes into a store, and the linen catches fire, and the store is burnt, that is obligated in full damage even though it also is the “arrows of the camel.”