
Actually it doesn't even mean that. A registered breeder is one that breeds five or more litters a year (or is otherwise considered to be breeding as a business). the law does require that they cannot breed from a bitch under a year old, and more often than at annual intervals.
It is up to the local authority to check that they comply with the regulations, but sadly a lot of cxommercial breeders issued with licenses are given little in the way of checks, and some have appaling conditions.
Most breeders that breed for breed improvement and for the love of their breed breed a lot less than five litters a year, unless they are involved with several breeds (say several family members) and have breeds with small litters, like the toy breeds.
Breeding a litter and socialising the pups properly, then choosing and interviewing prospective new owners is physically and emotionally taxing, you then need to keep availble to help with the pups in their new homes, so this precludes breeding lots of pups. :D