An ordinary household companion dog travelling with its owner. The most popular family dogs in the world are large breeds, the Labrador Retriever and the Golden Retriever among them, and those are precisely the dogs that hotel weight limits tend to exclude.
For the purposes of this standard, the family dog benchmark is a Labrador-sized dog: up to around 35 kg (77 lb) and 60 cm (24 in) at the shoulder, comparable to a Labrador Retriever, Golden Retriever, or Standard Poodle. It is a reference point, not a breed list and not a minimum. A policy that comfortably admits a dog of this size admits virtually every family dog, large or small. The benchmark matters because weight caps set below it, a common dogs under 10 kg only for instance, exclude the most popular family dogs there are.
A size or weight limit that would shut out an ordinary family dog, with no reason stated in the provider's published policy, is the kind of arbitrary restriction this standard exists to surface.